snpgdsPCASampLoading {SNPRelate} | R Documentation

## Project individuals onto existing principal component axes

### Description

To calculate the sample eigenvectors using the specified SNP loadings

### Usage

    snpgdsPCASampLoading(loadobj, gdsobj, sample.id=NULL, num.thread=1L,
        verbose=TRUE)

### Arguments

`loadobj` | a `snpgdsPCASNPLoadingClass` or `snpgdsEigMixSNPLoadingClass` object returned from snpgdsPCASNPLoading
`gdsobj` | an object of class `SNPGDSFileClass`, a SNP GDS file
`sample.id` | a vector of sample id specifying selected samples; if NULL, all samples are used
`num.thread` | the number of CPU cores used
`verbose` | if TRUE, show information

### Details

The `sample.id` are usually different from the samples used in the calculation of SNP loadings.

### Value

Returns a `snpgdsPCAClass` object, and it is a list:

`sample.id` | the sample ids used in the analysis
`snp.id` | the SNP ids used in the analysis
`eigenval` | eigenvalues
`eigenvect` | eigenvactors, “# of samples” x “eigen.cnt”
`TraceXTX` | the trace of the genetic covariance matrix
`Bayesian` | whether use bayerisan normalization

Or returns a `snpgdsEigMixClass` object, and it is a list:

`sample.id` | the sample ids used in the analysis
`snp.id` | the SNP ids used in the analysis
`eigenval` | eigenvalues
`eigenvect` | eigenvactors, “# of samples” x “eigen.cnt”
`afreq` | allele frequencies

### Author(s)

Xiuwen Zheng

### References

Patterson N, Price AL, Reich D (2006) Population structure and eigenanalysis. PLoS Genetics 2:e190.

Zhu, X., Li, S., Cooper, R. S., and Elston, R. C. (2008). A unified association analysis approach for family and unrelated samples correcting for stratification. Am J Hum Genet, 82(2), 352-365.

### See Also

`snpgdsPCA`, `snpgdsPCACorr`, `snpgdsPCASNPLoading`

### Examples

    # open an example dataset (HapMap)
    genofile <- snpgdsOpen(snpgdsExampleFileName())

    sample.id <- read.gdsn(index.gdsn(genofile, "sample.id"))

    # first PCA
    pca <- snpgdsPCA(genofile, eigen.cnt=8)
    snp_load <- snpgdsPCASNPLoading(pca, genofile)

    # calculate sample eigenvectors from SNP loadings
    samp_load <- snpgdsPCASampLoading(snp_load, genofile, sample.id=sample.id[1:100])

    diff <- pca$eigenvect[1:100,] - samp_load$eigenvect
    summary(c(diff))
    # ~ ZERO

    # combine eigenvectors
    allpca <- list(
        sample.id = c(pca$sample.id, samp_load$sample.id),
        snp.id = pca$snp.id,
        eigenval = c(pca$eigenval, samp_load$eigenval),
        eigenvect = rbind(pca$eigenvect, samp_load$eigenvect),
        varprop = c(pca$varprop, samp_load$varprop),
        TraceXTX = pca$TraceXTX
    )
    class(allpca) <- "snpgdsPCAClass"
    allpca

    # close the genotype file
    snpgdsClose(genofile)

[Package SNPRelate version 1.26.0 Index]