Run Canek on a toy example

In Canek: Batch Correction of Single Cell Transcriptome Data

knitr::opts_chunk$set(
  fig.width = 5,
  fig.height = 5,
  fig.align = "center",
  collapse = TRUE,
  comment = "#>"
)

library(Canek)

# Functions
## Function to plot the pca coordinates
plotPCA <- function(pcaData = NULL, label = NULL, legPosition = "topleft"){
  col <- as.integer(label) 
  plot(x = pcaData[,"PC1"], y = pcaData[,"PC2"],
       col = as.integer(label), cex = 0.75, pch = 19,
       xlab = "PC1", ylab = "PC2")
  legend(legPosition,  pch = 19,
         legend = levels(label), 
         col =  unique(as.integer(label)))
}

Load the data

On this toy example we use the two simulated batches included in the SimBatches data from Canek's package. SimBatches is a list containing:

• batches: Simulated scRNA-seq datasets with genes (rows) and cells (columns). Simulations were performed using Splatter.
• cell_type: a factor containing the celltype labels of the batches

lsData <- list(B1 = SimBatches$batches[[1]], B2 = SimBatches$batches[[2]])
batch <- factor(c(rep("Batch-1", ncol(lsData[[1]])),
                  rep("Batch-2", ncol(lsData[[2]]))))
celltype <- SimBatches$cell_types
table(batch)
table(celltype)

PCA before correction

We perform the Principal Component Analysis (PCA) of the joined datasets and scatter plot the first two PCs. The batch-effect causes cells to group by batch.

data <- Reduce(cbind, lsData)
pcaData <- prcomp(t(data), center = TRUE, scale. = TRUE)$x

plotPCA(pcaData = pcaData, label = batch, legPosition = "bottomleft")
plotPCA(pcaData = pcaData, label = celltype, legPosition = "bottomleft")

Run Canek

We correct the toy batches using the function RunCanek. This function accepts:

• List of matrices
• Seurat object
• List of Seurat objects
• SingleCellExperiment object
• List of SingleCellExperiment objects

On this example we use the list of matrices created before.

data <- RunCanek(lsData)

PCA after correction

We perform PCA of the corrected datasets and plot the first two PCs. After correction, the cells group by their corresponding cell type.

pcaData <- prcomp(t(data), center = TRUE, scale. = TRUE)$x

plotPCA(pcaData = pcaData, label = batch, legPosition = "topleft")
plotPCA(pcaData = pcaData, label = celltype, legPosition = "topleft")

Session info

sessionInfo()

Canek documentation built on Nov. 6, 2023, 1:06 a.m.