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Recover intra-sample doublets

Source: R/recoverDoublets.R
recoverDoublets.Rd

Recover intra-sample doublets that are neighbors to known inter-sample doublets in a multiplexed experiment.

Usage

recoverDoublets(x, ...)

# S4 method for class 'ANY'
recoverDoublets(
  x,
  doublets,
  samples,
  k = 50,
  transposed = FALSE,
  subset.row = NULL,
  BNPARAM = KmknnParam(),
  BPPARAM = SerialParam()
)

# S4 method for class 'SummarizedExperiment'
recoverDoublets(x, ..., assay.type = "logcounts")

# S4 method for class 'SingleCellExperiment'
recoverDoublets(x, ..., use.dimred = NULL)

Arguments

x

A log-expression matrix for all cells (including doublets) in columns and genes in rows. If transposed=TRUE, this should be a matrix of low-dimensional coordinates where each row corresponds to a cell.

Alternatively, a SummarizedExperiment or SingleCellExperiment containing (i) a log-expression matrix in the assays as specified by assay.type, or (ii) a matrix of reduced dimensions in the reducedDims as specified by use.dimred.

...

For the generic, additional arguments to pass to specific methods.

For the SummarizedExperiment method, additional arguments to pass to the ANY method.

For the SingleCellExperiment method, additional arguments to pass to the SummarizedExperiment method.

doublets

A logical, integer or character vector specifying which cells in x are known (inter-sample) doublets.

samples

A numeric vector containing the relative proportions of cells from each sample, used to determine how many cells are to be considered as intra-sample doublets.

k

Integer scalar specifying the number of nearest neighbors to use for computing the local doublet proportions.

transposed

Logical scalar indicating whether x is transposed, i.e., cells in the rows.

subset.row

A logical, integer or character vector specifying the genes to use for the neighbor search. Only used when transposed=FALSE.

BNPARAM

A BiocNeighborParam object specifying the algorithm to use for the nearest neighbor search.

BPPARAM

A BiocParallelParam object specifying the parallelization to use for the nearest neighbor search.

assay.type

A string specifying which assay values contain the log-expression matrix.

use.dimred

A string specifying whether existing values in reducedDims(x) should be used.

Value

A DataFrame containing one row per cell and the following fields:

  • proportion, a numeric field containing the proportion of neighbors that are doublets.

  • known, a logical field indicating whether this cell is a known inter-sample doublet.

  • predicted, a logical field indicating whether this cell is a predicted intra-sample doublet.

The metadata contains intra, a numeric scalar containing the expected number of intra-sample doublets.

Details

In multiplexed single-cell experiments, we can detect doublets as libraries with labels for multiple samples. However, this approach fails to identify doublets consisting of two cells with the same label. Such cells may be problematic if they are still sufficiently abundant to drive formation of spurious clusters.

This function identifies intra-sample doublets based on the similarity in expression profiles to known inter-sample doublets. For each cell, we compute the proportion of the k neighbors that are known doublets. Of the “unmarked” cells that are not known doublets, those with top \(X\) largest proportions are considered to be intra-sample doublets. We use samples to obtain a reasonable estimate for \(X\), see the vignette for details.

A larger value of k provides more stable estimates of the doublet proportion in each cell. However, this comes at the cost of assuming that each cell actually has k neighboring cells of the same state. For example, if a doublet cluster has fewer than k members, its doublet proportions will be “diluted” by inclusion of unmarked cells in the next-closest cluster.

See also

doubletCells and doubletCluster, for alternative methods of doublet detection when no prior doublet information is available.

hashedDrops from the DropletUtils package, to identify doublets from cell hashing experiments.

More detail on the mathematical background of this function is provided in the corresponding vignette at vignette("recoverDoublets", package="scDblFinder").

Author

Aaron Lun

Examples

# Mocking up an example.
set.seed(100)
ngenes <- 1000
mu1 <- 2^rnorm(ngenes, sd=2)
mu2 <- 2^rnorm(ngenes, sd=2)

counts.1 <- matrix(rpois(ngenes*100, mu1), nrow=ngenes) # Pure type 1
counts.2 <- matrix(rpois(ngenes*100, mu2), nrow=ngenes) # Pure type 2
counts.m <- matrix(rpois(ngenes*20, mu1+mu2), nrow=ngenes) # Doublets (1 & 2)
all.counts <- cbind(counts.1, counts.2, counts.m)
lcounts <- scuttle::normalizeCounts(all.counts)

# Pretending that half of the doublets are known. Also pretending that 
# the experiment involved two samples of equal size.
known <- 200 + seq_len(10) 
out <- recoverDoublets(lcounts, doublets=known, k=10, samples=c(1, 1))
out
#> DataFrame with 220 rows and 3 columns
#>     proportion     known predicted
#>      <numeric> <logical> <logical>
#> 1            0     FALSE     FALSE
#> 2            0     FALSE     FALSE
#> 3            0     FALSE     FALSE
#> 4            0     FALSE     FALSE
#> 5            0     FALSE     FALSE
#> ...        ...       ...       ...
#> 216        0.5     FALSE      TRUE
#> 217        0.5     FALSE      TRUE
#> 218        0.4     FALSE      TRUE
#> 219        0.3     FALSE      TRUE
#> 220        0.4     FALSE      TRUE