benchmarks/quantile_position.md
In charles-plessy/CAGEr: Analysis of CAGE (Cap Analysis of Gene Expression) sequencing data for precise mapping of transcription start sites and promoterome mining
title: "Quantile positions in cumulative sums"
author: "Charles Plessy"
date: "2023-06-30"
output:
html_document:
keep_md: yes
editor_options:
chunk_output_type: console
Purpose
The function to determine quantile positions is one of the slowest in CAGEr.
Can we speed it up?
Setup
library("CAGEr") |> suppressPackageStartupMessages()
library("ggplot2") |> suppressPackageStartupMessages()
Example data
cum.sums <- CTSScumulativesTagClusters(exampleCAGEexp)[[1]]
clusters <- tagClustersGR(exampleCAGEexp)[[1]]
Current implementation at the time the benchmark was written.
getQuantilepos_Vectorized_tail_decoded <- Vectorize(vectorize.args = "cum.sum", function(q, cum.sum) {
cum.sum <- decode(cum.sum) # A microbenchmark showed it it 3 times faster when applying decode() now
c.max <- tail(cum.sum,1) # Max is last element since x is a cumulative sums.
treshold <- c.max * q
which.max(cum.sum >= treshold)
})
getQuantilepos_Vectorized_tail_decoded(.9, cum.sums) |> head()
## 1 2 3 4 5 6
## 1 1 1 1 72 1
Alternative functions.
getQuantilepos_Vectorized_tail <- Vectorize(vectorize.args = "cum.sum", function(q, cum.sum) {
c.max <- tail(cum.sum,1) # Max is last element since x is a cumulative sums.
treshold <- c.max * q
which.max(cum.sum >= treshold)
})
getQuantilepos_Vectorized_tail(.9, cum.sums) |> head()
## 1 2 3 4 5 6
## 1 1 1 1 72 1
getQuantilepos_Vectorized_max_decoded <- Vectorize(vectorize.args = "cum.sum", function(q, cum.sum) {
cum.sum <- decode(cum.sum)
c.max <- max(cum.sum) # Max is last element since x is a cumulative sums.
treshold <- c.max * q
which.max(cum.sum >= treshold)
})
getQuantilepos_Vectorized_max_decoded(.9, cum.sums) |> head()
## 1 2 3 4 5 6
## 1 1 1 1 72 1
getQuantilepos_Vectorized_max <- Vectorize(vectorize.args = "cum.sum", function(q, cum.sum) {
c.max <- max(cum.sum) # Max is last element since x is a cumulative sums.
treshold <- c.max * q
which.max(cum.sum >= treshold)
})
getQuantilepos_Vectorized_max(.9, cum.sums) |> head()
## 1 2 3 4 5 6
## 1 1 1 1 72 1
getQuantilepos_lapply <- function(q, cum.sums, decode = FALSE) {
if (isTRUE(decode)) cum.sums <- lapply(cum.sums, decode)
l <- sapply(cum.sums, \(cum.sum) {
c.max <- tail(cum.sum,1) # Max is last element since x is a cumulative sums.
treshold <- c.max * q
which.max(cum.sum >= treshold)})
l
}
getQuantilepos_lapply(.9, cum.sums) |> head()
## 1 2 3 4 5 6
## 1 1 1 1 72 1
getQuantilepos_Rle_native <- function(q, cum.sums) {
(cum.sums >= max(cum.sums) * q )|> sapply(which.max)
}
getQuantilepos_Rle_native(.9, cum.sums) |> head()
## 1 2 3 4 5 6
## 1 1 1 1 72 1
getQuantilepos_NL_native <- function(q, cum.sums) {
nl <- as(cum.sums, "NumericList")
min(which(nl >= max(nl) * q))
}
getQuantilepos_NL_native(.9, cum.sums) |> head()
## 1 2 3 4 5 6
## 1 1 1 1 72 1
getQuantilepos_ChatGPT <- function(q, cum.sums, decode = FALSE) {
if (isTRUE(decode)) cum.sums <- lapply(cum.sums, decode)
find_quantile_and_index <- function(x, q) {
# Interestingly ChatGPT's definition of quantiles appears more sound,
# quantile_value <- quantile(x, q)
# But the definition below is the one orgiginally used in CAGEr.
quantile_value <- max(x) * q
which(x >= quantile_value)[1]
}
sapply(cum.sums, find_quantile_and_index, q)
}
getQuantilepos_ChatGPT(.9, cum.sums) |> head()
## 1 2 3 4 5 6
## 1 1 1 1 72 1
Benchmark
(microbench_out <- microbenchmark::microbenchmark(
times = 100,
Vectorized_tail_decoded = getQuantilepos_Vectorized_tail_decoded(.9, cum.sums),
Vectorized_tail = getQuantilepos_Vectorized_tail(.9, cum.sums),
Vectorized_max_decoded = getQuantilepos_Vectorized_max_decoded(.9, cum.sums),
Vectorized_max = getQuantilepos_Vectorized_max(.9, cum.sums),
lapply = getQuantilepos_lapply(.9, cum.sums),
lapply_decoded = getQuantilepos_lapply(.9, cum.sums, decode = TRUE),
Rle_native = getQuantilepos_Rle_native(.9, cum.sums),
NL_native = getQuantilepos_NL_native(.9, cum.sums),
ChatGPT = getQuantilepos_ChatGPT(.9, cum.sums),
ChatGPT_decoded = getQuantilepos_ChatGPT(.9, cum.sums, decode = TRUE)
))
## Unit: milliseconds
## expr min lq mean median
## Vectorized_tail_decoded 226.829726 234.819918 286.97939 253.23864
## Vectorized_tail 684.732639 735.672604 904.44242 827.81918
## Vectorized_max_decoded 220.561623 226.360906 286.71244 250.03909
## Vectorized_max 425.882113 451.098007 585.66493 511.43531
## lapply 1218.524937 1358.116061 1578.09167 1482.08125
## lapply_decoded 679.861133 735.194260 879.32682 817.87322
## Rle_native 675.975803 718.836427 838.95589 779.28237
## NL_native 9.486656 9.942683 11.53794 10.42981
## ChatGPT 952.030342 1015.902702 1277.46268 1122.26911
## ChatGPT_decoded 677.942011 742.759078 875.11836 816.32189
## uq max neval
## 294.79168 700.34834 100
## 896.60301 1709.49658 100
## 301.12672 892.87669 100
## 655.94249 1334.79107 100
## 1602.81593 3465.68446 100
## 912.35238 2064.05496 100
## 872.24652 2335.11442 100
## 11.83217 26.55179 100
## 1345.28727 7607.42296 100
## 890.72910 1632.77436 100
# https://statisticsglobe.com/microbenchmark-package-r
ggplot(microbench_out, aes(x = time / 1e9, y = expr, color = expr)) + # Plot performance comparison
geom_boxplot() +
scale_x_log10("time (seconds)")
Result
The winner is 20 times faster!
getQuantilepos_NL_native <- function(q, cum.sums) {
nl <- as(cum.sums, "NumericList")
min(which(nl >= max(nl) * q))
}
identical(
getQuantilepos_Vectorized_tail_decoded(.9, cum.sums),
getQuantilepos_NL_native(.9, cum.sums)
)
## [1] TRUE
Session information
sessionInfo()
## R version 4.3.0 (2023-04-21)
## Platform: x86_64-pc-linux-gnu (64-bit)
## Running under: Debian GNU/Linux 12 (bookworm)
##
## Matrix products: default
## BLAS: /usr/lib/x86_64-linux-gnu/blas/libblas.so.3.11.0
## LAPACK: /usr/lib/x86_64-linux-gnu/lapack/liblapack.so.3.11.0
##
## locale:
## [1] LC_CTYPE=en_US.UTF-8 LC_NUMERIC=C
## [3] LC_TIME=en_US.UTF-8 LC_COLLATE=en_US.UTF-8
## [5] LC_MONETARY=en_US.UTF-8 LC_MESSAGES=en_US.UTF-8
## [7] LC_PAPER=en_US.UTF-8 LC_NAME=C
## [9] LC_ADDRESS=C LC_TELEPHONE=C
## [11] LC_MEASUREMENT=en_US.UTF-8 LC_IDENTIFICATION=C
##
## time zone: Etc/UTC
## tzcode source: system (glibc)
##
## attached base packages:
## [1] stats4 stats graphics grDevices utils datasets methods
## [8] base
##
## other attached packages:
## [1] ggplot2_3.4.2 CAGEr_2.6.0
## [3] MultiAssayExperiment_1.26.0 SummarizedExperiment_1.30.2
## [5] Biobase_2.60.0 GenomicRanges_1.52.0
## [7] GenomeInfoDb_1.36.1 IRanges_2.34.1
## [9] S4Vectors_0.38.1 BiocGenerics_0.46.0
## [11] MatrixGenerics_1.12.2 matrixStats_1.0.0
##
## loaded via a namespace (and not attached):
## [1] RColorBrewer_1.1-3 rstudioapi_0.14
## [3] jsonlite_1.8.5 magrittr_2.0.3
## [5] GenomicFeatures_1.52.1 farver_2.1.1
## [7] rmarkdown_2.22 BiocIO_1.10.0
## [9] zlibbioc_1.46.0 vctrs_0.6.2
## [11] memoise_2.0.1 Rsamtools_2.16.0
## [13] DelayedMatrixStats_1.22.1 RCurl_1.98-1.12
## [15] base64enc_0.1-3 htmltools_0.5.5
## [17] S4Arrays_1.0.4 progress_1.2.2
## [19] curl_5.0.1 Formula_1.2-5
## [21] sass_0.4.6 KernSmooth_2.23-20
## [23] bslib_0.5.0 htmlwidgets_1.6.2
## [25] plyr_1.8.8 Gviz_1.44.0
## [27] cachem_1.0.8 GenomicAlignments_1.36.0
## [29] lifecycle_1.0.3 pkgconfig_2.0.3
## [31] Matrix_1.5-3 R6_2.5.1
## [33] fastmap_1.1.1 GenomeInfoDbData_1.2.10
## [35] digest_0.6.31 colorspace_2.1-0
## [37] AnnotationDbi_1.62.1 Hmisc_5.1-0
## [39] RSQLite_2.3.1 vegan_2.6-4
## [41] filelock_1.0.2 fansi_1.0.4
## [43] mgcv_1.8-41 httr_1.4.6
## [45] compiler_4.3.0 microbenchmark_1.4.10
## [47] withr_2.5.0 bit64_4.0.5
## [49] htmlTable_2.4.1 backports_1.4.1
## [51] CAGEfightR_1.20.0 BiocParallel_1.34.2
## [53] DBI_1.1.3 highr_0.10
## [55] biomaRt_2.56.1 MASS_7.3-58.2
## [57] rappdirs_0.3.3 DelayedArray_0.26.5
## [59] rjson_0.2.21 permute_0.9-7
## [61] gtools_3.9.4 tools_4.3.0
## [63] foreign_0.8-84 nnet_7.3-18
## [65] glue_1.6.2 restfulr_0.0.15
## [67] nlme_3.1-162 stringdist_0.9.10
## [69] grid_4.3.0 checkmate_2.2.0
## [71] reshape2_1.4.4 cluster_2.1.4
## [73] generics_0.1.3 operator.tools_1.6.3
## [75] gtable_0.3.3 BSgenome_1.68.0
## [77] formula.tools_1.7.1 ensembldb_2.24.0
## [79] data.table_1.14.8 hms_1.1.3
## [81] xml2_1.3.4 utf8_1.2.3
## [83] XVector_0.40.0 pillar_1.9.0
## [85] stringr_1.5.0 splines_4.3.0
## [87] dplyr_1.1.2 BiocFileCache_2.8.0
## [89] lattice_0.20-45 rtracklayer_1.60.0
## [91] bit_4.0.5 deldir_1.0-9
## [93] biovizBase_1.48.0 tidyselect_1.2.0
## [95] Biostrings_2.68.1 knitr_1.43
## [97] gridExtra_2.3 ProtGenerics_1.32.0
## [99] xfun_0.39 stringi_1.7.12
## [101] VGAM_1.1-8 lazyeval_0.2.2
## [103] yaml_2.3.7 som_0.3-5.1
## [105] evaluate_0.21 codetools_0.2-19
## [107] interp_1.1-4 tibble_3.2.1
## [109] cli_3.6.1 rpart_4.1.19
## [111] munsell_0.5.0 jquerylib_0.1.4
## [113] dichromat_2.0-0.1 Rcpp_1.0.10
## [115] dbplyr_2.3.2 png_0.1-8
## [117] XML_3.99-0.14 parallel_4.3.0
## [119] assertthat_0.2.1 blob_1.2.4
## [121] prettyunits_1.1.1 latticeExtra_0.6-30
## [123] jpeg_0.1-10 AnnotationFilter_1.24.0
## [125] sparseMatrixStats_1.12.1 bitops_1.0-7
## [127] VariantAnnotation_1.46.0 scales_1.2.1
## [129] crayon_1.5.2 rlang_1.1.1
## [131] KEGGREST_1.40.0
ChatGPT
Charles 10:15 AM
Good morning ChatGPT
APP 10:15 AM
Good morning! How can I assist you today?
Charles 10:17 AM
Using the R programming language, I want to find in a list of vectors of sorted numerical values the index where the value exceeds a given quantile.
APP 10:17 AM
In R programming, you can use the which function in combination with the quantile function to find the index in a list of sorted numerical vectors where the value exceeds a given quantile. Here's an example:
r
# Assume 'v' is your sorted numerical vector
v <- c(1, 2, 3, 4, 5, 6, 7, 8, 9, 10)
# Define your quantile, for example, the 50th percentile (median)
q <- quantile(v, 0.5)
# Find the indices where the value exceeds the quantile
indices <- which(v > q)
# Print the indices
print(indices)
This will give you the indices of the values in the vector 'v' that are greater than the 50th percentile. You can adjust the quantile value as needed.
Charles 10:18 AM
Thanks, the vectors are in a list, and I need to run the function on each of them in an efficient way. Can you write a vectorized function?
APP 10:18 AM
In R programming, you can use the lapply function in combination with which and quantile to create a vectorized function that finds the index in each vector of a list where the value exceeds a given quantile. Here's an example:
r
# Define your list of vectors
list_of_vectors <- list(c(1,2,3,4,5), c(6,7,8,9,10), c(11,12,13,14,15))
# Define the quantile
q <- 0.75
# Define the function
find_index <- function(x, q) {
return(which(x > quantile(x, q)))
}
# Apply the function to each vector in the list
result <- lapply(list_of_vectors, find_index, q)
# Print the result
print(result)
In this example, find_index is a function that takes a vector and a quantile as input, and returns the indices of the vector where the value exceeds the given quantile. The lapply function applies this function to each vector in the list. The result is a list of vectors, where each vector contains the indices where the value exceeds the given quantile.
Charles 10:19 AM
Thanks, we are almost there. I want the function to compute the quantile specifically on each vector.
APP 10:19 AM
In R programming, you can use the lapply() function to apply a function to each element of a list. If you want to compute the quantile for each vector in the list, you can do it like this:
r
# Assuming 'my_list' is your list of vectors
result <- lapply(my_list, function(x) quantile(x, probs = c(0.25, 0.5, 0.75)))
This will return a new list where each element is the 25th, 50th, and 75th percentile of the corresponding vector in the original list. You can modify the probs parameter to compute different quantiles.
Charles 10:21 AM
Sorry, but what I mean is: I have a list of vectors, and for each vector of that list I need to find a given quantile, and the first index as which the value in the vector exceed the quantile.
APP 10:21 AM
In R, you can use the lapply function to apply a function to each element in a list. Here's how you can find for each vector in a list, a given quantile, and the first index at which the value in the vector exceeds the quantile:
r
# Assume 'lst' is your list of vectors and 'q' is your quantile
lst <- list(c(1,2,3,4,5), c(6,7,8,9,10), c(11,12,13,14,15))
q <- 0.5
# Function to calculate quantile and find the first index exceeding the quantile
find_quantile_and_index <- function(x, q) {
quantile_value <- quantile(x, q)
index <- which(x > quantile_value)[1]
return(list("quantile" = quantile_value, "index" = index))
}
# Apply the function to each vector in the list
result <- lapply(lst, find_quantile_and_index, q)
# Print the result
print(result)
This will return a list of lists, where each sub-list contains the quantile and the first index at which the value in the vector exceeds the quantile for each vector in the original list.
Charles 10:29 AM
Thanks, but it is too slow in my benchmark. Can you propose me a faster version ?
APP 10:29 AM
To optimize your function in R, you can use the lapply function which is faster than loops. Here's an example:
r
# Assuming 'lst' is your list of vectors and 'q' is your quantile
results <- lapply(lst, function(x) {
quantile_val <- quantile(x, q)
index <- which(x > quantile_val)[1]
return(list("quantile" = quantile_val, "index" = index))
})
This function applies the anonymous function to each vector in the list. The function calculates the quantile, finds the first index where the value exceeds the quantile, and returns them as a list. The result is a list of these lists.
Remember, R is vectorized which means it's more efficient to apply a function to a whole vector at once rather than element by element. Functions like lapply take advantage of this. Also, using which with the condition directly is faster than looping through the vector to find the index.
charles-plessy/CAGEr documentation built on Oct. 27, 2024, 10:11 p.m.
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title: "Quantile positions in cumulative sums" author: "Charles Plessy" date: "2023-06-30" output: html_document: keep_md: yes editor_options: chunk_output_type: console
Purpose
The function to determine quantile positions is one of the slowest in CAGEr. Can we speed it up?
Setup
library("CAGEr") |> suppressPackageStartupMessages()
library("ggplot2") |> suppressPackageStartupMessages()
Example data
cum.sums <- CTSScumulativesTagClusters(exampleCAGEexp)[[1]]
clusters <- tagClustersGR(exampleCAGEexp)[[1]]
Current implementation at the time the benchmark was written.
getQuantilepos_Vectorized_tail_decoded <- Vectorize(vectorize.args = "cum.sum", function(q, cum.sum) {
cum.sum <- decode(cum.sum) # A microbenchmark showed it it 3 times faster when applying decode() now
c.max <- tail(cum.sum,1) # Max is last element since x is a cumulative sums.
treshold <- c.max * q
which.max(cum.sum >= treshold)
})
getQuantilepos_Vectorized_tail_decoded(.9, cum.sums) |> head()
## 1 2 3 4 5 6
## 1 1 1 1 72 1
Alternative functions.
getQuantilepos_Vectorized_tail <- Vectorize(vectorize.args = "cum.sum", function(q, cum.sum) {
c.max <- tail(cum.sum,1) # Max is last element since x is a cumulative sums.
treshold <- c.max * q
which.max(cum.sum >= treshold)
})
getQuantilepos_Vectorized_tail(.9, cum.sums) |> head()
## 1 2 3 4 5 6
## 1 1 1 1 72 1
getQuantilepos_Vectorized_max_decoded <- Vectorize(vectorize.args = "cum.sum", function(q, cum.sum) {
cum.sum <- decode(cum.sum)
c.max <- max(cum.sum) # Max is last element since x is a cumulative sums.
treshold <- c.max * q
which.max(cum.sum >= treshold)
})
getQuantilepos_Vectorized_max_decoded(.9, cum.sums) |> head()
## 1 2 3 4 5 6
## 1 1 1 1 72 1
getQuantilepos_Vectorized_max <- Vectorize(vectorize.args = "cum.sum", function(q, cum.sum) {
c.max <- max(cum.sum) # Max is last element since x is a cumulative sums.
treshold <- c.max * q
which.max(cum.sum >= treshold)
})
getQuantilepos_Vectorized_max(.9, cum.sums) |> head()
## 1 2 3 4 5 6
## 1 1 1 1 72 1
getQuantilepos_lapply <- function(q, cum.sums, decode = FALSE) {
if (isTRUE(decode)) cum.sums <- lapply(cum.sums, decode)
l <- sapply(cum.sums, \(cum.sum) {
c.max <- tail(cum.sum,1) # Max is last element since x is a cumulative sums.
treshold <- c.max * q
which.max(cum.sum >= treshold)})
l
}
getQuantilepos_lapply(.9, cum.sums) |> head()
## 1 2 3 4 5 6
## 1 1 1 1 72 1
getQuantilepos_Rle_native <- function(q, cum.sums) {
(cum.sums >= max(cum.sums) * q )|> sapply(which.max)
}
getQuantilepos_Rle_native(.9, cum.sums) |> head()
## 1 2 3 4 5 6
## 1 1 1 1 72 1
getQuantilepos_NL_native <- function(q, cum.sums) {
nl <- as(cum.sums, "NumericList")
min(which(nl >= max(nl) * q))
}
getQuantilepos_NL_native(.9, cum.sums) |> head()
## 1 2 3 4 5 6
## 1 1 1 1 72 1
getQuantilepos_ChatGPT <- function(q, cum.sums, decode = FALSE) {
if (isTRUE(decode)) cum.sums <- lapply(cum.sums, decode)
find_quantile_and_index <- function(x, q) {
# Interestingly ChatGPT's definition of quantiles appears more sound,
# quantile_value <- quantile(x, q)
# But the definition below is the one orgiginally used in CAGEr.
quantile_value <- max(x) * q
which(x >= quantile_value)[1]
}
sapply(cum.sums, find_quantile_and_index, q)
}
getQuantilepos_ChatGPT(.9, cum.sums) |> head()
## 1 2 3 4 5 6
## 1 1 1 1 72 1
Benchmark
(microbench_out <- microbenchmark::microbenchmark(
times = 100,
Vectorized_tail_decoded = getQuantilepos_Vectorized_tail_decoded(.9, cum.sums),
Vectorized_tail = getQuantilepos_Vectorized_tail(.9, cum.sums),
Vectorized_max_decoded = getQuantilepos_Vectorized_max_decoded(.9, cum.sums),
Vectorized_max = getQuantilepos_Vectorized_max(.9, cum.sums),
lapply = getQuantilepos_lapply(.9, cum.sums),
lapply_decoded = getQuantilepos_lapply(.9, cum.sums, decode = TRUE),
Rle_native = getQuantilepos_Rle_native(.9, cum.sums),
NL_native = getQuantilepos_NL_native(.9, cum.sums),
ChatGPT = getQuantilepos_ChatGPT(.9, cum.sums),
ChatGPT_decoded = getQuantilepos_ChatGPT(.9, cum.sums, decode = TRUE)
))
## Unit: milliseconds
## expr min lq mean median
## Vectorized_tail_decoded 226.829726 234.819918 286.97939 253.23864
## Vectorized_tail 684.732639 735.672604 904.44242 827.81918
## Vectorized_max_decoded 220.561623 226.360906 286.71244 250.03909
## Vectorized_max 425.882113 451.098007 585.66493 511.43531
## lapply 1218.524937 1358.116061 1578.09167 1482.08125
## lapply_decoded 679.861133 735.194260 879.32682 817.87322
## Rle_native 675.975803 718.836427 838.95589 779.28237
## NL_native 9.486656 9.942683 11.53794 10.42981
## ChatGPT 952.030342 1015.902702 1277.46268 1122.26911
## ChatGPT_decoded 677.942011 742.759078 875.11836 816.32189
## uq max neval
## 294.79168 700.34834 100
## 896.60301 1709.49658 100
## 301.12672 892.87669 100
## 655.94249 1334.79107 100
## 1602.81593 3465.68446 100
## 912.35238 2064.05496 100
## 872.24652 2335.11442 100
## 11.83217 26.55179 100
## 1345.28727 7607.42296 100
## 890.72910 1632.77436 100
# https://statisticsglobe.com/microbenchmark-package-r
ggplot(microbench_out, aes(x = time / 1e9, y = expr, color = expr)) + # Plot performance comparison
geom_boxplot() +
scale_x_log10("time (seconds)")
Result
The winner is 20 times faster!
getQuantilepos_NL_native <- function(q, cum.sums) {
nl <- as(cum.sums, "NumericList")
min(which(nl >= max(nl) * q))
}
identical(
getQuantilepos_Vectorized_tail_decoded(.9, cum.sums),
getQuantilepos_NL_native(.9, cum.sums)
)
## [1] TRUE
Session information
sessionInfo()
## R version 4.3.0 (2023-04-21)
## Platform: x86_64-pc-linux-gnu (64-bit)
## Running under: Debian GNU/Linux 12 (bookworm)
##
## Matrix products: default
## BLAS: /usr/lib/x86_64-linux-gnu/blas/libblas.so.3.11.0
## LAPACK: /usr/lib/x86_64-linux-gnu/lapack/liblapack.so.3.11.0
##
## locale:
## [1] LC_CTYPE=en_US.UTF-8 LC_NUMERIC=C
## [3] LC_TIME=en_US.UTF-8 LC_COLLATE=en_US.UTF-8
## [5] LC_MONETARY=en_US.UTF-8 LC_MESSAGES=en_US.UTF-8
## [7] LC_PAPER=en_US.UTF-8 LC_NAME=C
## [9] LC_ADDRESS=C LC_TELEPHONE=C
## [11] LC_MEASUREMENT=en_US.UTF-8 LC_IDENTIFICATION=C
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## time zone: Etc/UTC
## tzcode source: system (glibc)
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## attached base packages:
## [1] stats4 stats graphics grDevices utils datasets methods
## [8] base
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## other attached packages:
## [1] ggplot2_3.4.2 CAGEr_2.6.0
## [3] MultiAssayExperiment_1.26.0 SummarizedExperiment_1.30.2
## [5] Biobase_2.60.0 GenomicRanges_1.52.0
## [7] GenomeInfoDb_1.36.1 IRanges_2.34.1
## [9] S4Vectors_0.38.1 BiocGenerics_0.46.0
## [11] MatrixGenerics_1.12.2 matrixStats_1.0.0
##
## loaded via a namespace (and not attached):
## [1] RColorBrewer_1.1-3 rstudioapi_0.14
## [3] jsonlite_1.8.5 magrittr_2.0.3
## [5] GenomicFeatures_1.52.1 farver_2.1.1
## [7] rmarkdown_2.22 BiocIO_1.10.0
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ChatGPT
Charles 10:15 AM
Good morning ChatGPT
APP 10:15 AM
Good morning! How can I assist you today?
Charles 10:17 AM
Using the R programming language, I want to find in a list of vectors of sorted numerical values the index where the value exceeds a given quantile.
APP 10:17 AM
In R programming, you can use the
whichfunction in combination with thequantilefunction to find the index in a list of sorted numerical vectors where the value exceeds a given quantile. Here's an example:
r
# Assume 'v' is your sorted numerical vector
v <- c(1, 2, 3, 4, 5, 6, 7, 8, 9, 10)
# Define your quantile, for example, the 50th percentile (median)
q <- quantile(v, 0.5)
# Find the indices where the value exceeds the quantile
indices <- which(v > q)
# Print the indices
print(indices)
This will give you the indices of the values in the vector 'v' that are greater than the 50th percentile. You can adjust the quantile value as needed.
Charles 10:18 AM
Thanks, the vectors are in a list, and I need to run the function on each of them in an efficient way. Can you write a vectorized function?
APP 10:18 AM
In R programming, you can use the
lapplyfunction in combination with which and quantile to create a vectorized function that finds the index in each vector of a listwherethe value exceeds a givenquantile.Here's an example:
r
# Define your list of vectors
list_of_vectors <- list(c(1,2,3,4,5), c(6,7,8,9,10), c(11,12,13,14,15))
# Define the quantile
q <- 0.75
# Define the function
find_index <- function(x, q) {
return(which(x > quantile(x, q)))
}
# Apply the function to each vector in the list
result <- lapply(list_of_vectors, find_index, q)
# Print the result
print(result)
In this example,
find_indexis a function that takes a vector and a quantile as input, and returns the indices of the vector where the value exceeds the given quantile. Thelapplyfunction applies this function to each vector in the list. The result is a list of vectors, where each vector contains the indices where the value exceeds the given quantile.
Charles 10:19 AM
Thanks, we are almost there. I want the function to compute the quantile specifically on each vector.
APP 10:19 AM
In R programming, you can use the
lapply()function to apply a function to each element of a list. If you want to compute the quantile for each vector in the list, you can do it like this:
r
# Assuming 'my_list' is your list of vectors
result <- lapply(my_list, function(x) quantile(x, probs = c(0.25, 0.5, 0.75)))
This will return a new list where each element is the 25th, 50th, and 75th percentile of the corresponding vector in the original list. You can modify the
probsparameter to compute different quantiles.
Charles 10:21 AM
Sorry, but what I mean is: I have a list of vectors, and for each vector of that list I need to find a given quantile, and the first index as which the value in the vector exceed the quantile.
APP 10:21 AM
In R, you can use the
lapplyfunction to apply a function to each element in a list. Here's how you can find for each vector in a list, a given quantile, and the first index at which the value in the vector exceeds the quantile:
r
# Assume 'lst' is your list of vectors and 'q' is your quantile
lst <- list(c(1,2,3,4,5), c(6,7,8,9,10), c(11,12,13,14,15))
q <- 0.5
# Function to calculate quantile and find the first index exceeding the quantile
find_quantile_and_index <- function(x, q) {
quantile_value <- quantile(x, q)
index <- which(x > quantile_value)[1]
return(list("quantile" = quantile_value, "index" = index))
}
# Apply the function to each vector in the list
result <- lapply(lst, find_quantile_and_index, q)
# Print the result
print(result)
This will return a list of lists, where each sub-list contains the quantile and the first index at which the value in the vector exceeds the quantile for each vector in the original list.
Charles 10:29 AM
Thanks, but it is too slow in my benchmark. Can you propose me a faster version ? APP 10:29 AM
To optimize your function in R, you can use the
lapplyfunction which is faster than loops. Here's an example:
r
# Assuming 'lst' is your list of vectors and 'q' is your quantile
results <- lapply(lst, function(x) {
quantile_val <- quantile(x, q)
index <- which(x > quantile_val)[1]
return(list("quantile" = quantile_val, "index" = index))
})
This function applies the anonymous function to each vector in the list. The function calculates the quantile, finds the first index where the value exceeds the quantile, and returns them as a list. The result is a list of these lists.
Remember, R is vectorized which means it's more efficient to apply a function to a whole vector at once rather than element by element. Functions like
lapplytake advantage of this. Also, usingwhichwith the condition directly is faster than looping through the vector to find the index.
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