Description Usage Arguments Details Examples
multi_meta
returns the meta-analysis results for
multivariate GWAS across different cohorts.
1 2 3 | multi_meta(files = c(), N = c(),
output.file = "Meta_Results.txt", size.chunks = 5e+06,
min.pop = 2, sep = "\t")
|
files |
A vector containing the names of the results files to meta-analyse. These can be outputs from GEMMA multivariate analysis or similar (see Details). Furthermore they can be single-chromosome or genome-wide results. |
N |
A vector containing sample sizes for each of the above files. This parameter is optional and is only required for computing the overall allele frequency. |
output.file |
The name of the output file. |
size.chunks |
Size of each chunk to be read and processed. Default is 5,000,000 (5 Mb). This size will require very low memory usage. Increase this parameter if more memory is allocated or if the number of cohorts is limited. Read more about the chunks in Details. |
min.pop |
Minimum number of populations required per SNP to compute meta-analysis. Default is 2, it can be any number up to the total number of cohorts analysed. |
sep |
Separator for reading input files. |
This function applies an inverse-variance based method to meta-analyse multivariate GWAS results. In particular, given n different cohorts, for which p phenotypes have been tested for genome-wide association, the results for each cohort will have p different effect size coefficients i.e. beta values (one per each phenotype) and a variance/covariance pxp matrix representing beta's variances and covariances. In particular, the function is built to consider the output from the GEMMA software multivariate association testing. If your output is not produced with GEMMA, the function works on any results file containing the following column names:
chr Chromosome
ps Position
rs SNP name
allele1 Effect allele
allele0 Non-effect allele
af Effect-allele frequency
beta_1, beta_2, ..., beta_p Effect sizes for each of the p traits
Vbeta_1_1, Vbeta_1_2, ..., Vbeta_1_p, Vbeta_2_2, ..., Vbeta_2_p, ..., Vbeta_p_p variance-covariance matrix entries (diagonal and upper triangle values only, since this matrix is symmetric)
The function divides input files into chunks based on position. Only one chunk at a time is read and analysed; thus a limited amount of data is loaded in the workspace at one given time. Default chunk dimension is 5 Mb for which low memory is required (<250 MB for 2 cohorts). If you have larger RAM availability, sparse markers or a limited number of cohorts, change chunks' dimension from the command line.
1 2 3 4 | file1=system.file("extdata", "Example_file_1.txt", package="MultiMeta")
file2=system.file("extdata", "Example_file_2.txt", package="MultiMeta")
multi_meta(files=c(file1,file2), N=c(1200,600), sep=" ",
output.file="Output_from_running_example.txt")
|
Add the following code to your website.
For more information on customizing the embed code, read Embedding Snippets.