FindTransferAnchors {Seurat} | R Documentation |
Find transfer anchors
Description
Find a set of anchors between a reference and query object. These
anchors can later be used to transfer data from the reference to
query object using the TransferData
object.
Usage
FindTransferAnchors(
reference,
query,
normalization.method = "LogNormalize",
recompute.residuals = TRUE,
reference.assay = NULL,
reference.neighbors = NULL,
query.assay = NULL,
reduction = "pcaproject",
reference.reduction = NULL,
project.query = FALSE,
features = NULL,
scale = TRUE,
npcs = 30,
l2.norm = TRUE,
dims = 1:30,
k.anchor = 5,
k.filter = NA,
k.score = 30,
max.features = 200,
nn.method = "annoy",
n.trees = 50,
eps = 0,
approx.pca = TRUE,
mapping.score.k = NULL,
verbose = TRUE
)
Arguments
reference |
|
query |
|
normalization.method |
Name of normalization method used: LogNormalize or SCT. |
recompute.residuals |
If using SCT as a normalization method, compute query Pearson residuals using the reference SCT model parameters. |
reference.assay |
Name of the Assay to use from reference |
reference.neighbors |
Name of the Neighbor to use from the reference. Optionally enables reuse of precomputed neighbors. |
query.assay |
Name of the Assay to use from query |
reduction |
Dimensional reduction to perform when finding anchors. Options are:
|
reference.reduction |
Name of dimensional reduction to use from the reference if running the pcaproject workflow. Optionally enables reuse of precomputed reference dimensional reduction. If NULL (default), use a PCA computed on the reference object. |
project.query |
Project the PCA from the query dataset onto the reference. Use only in rare cases where the query dataset has a much larger cell number, but the reference dataset has a unique assay for transfer. In this case, the default features will be set to the variable features of the query object that are alos present in the reference. |
features |
Features to use for dimensional reduction. If not specified, set as variable features of the reference object which are also present in the query. |
scale |
Scale query data. |
npcs |
Number of PCs to compute on reference if reference.reduction is not provided. |
l2.norm |
Perform L2 normalization on the cell embeddings after dimensional reduction |
dims |
Which dimensions to use from the reduction to specify the neighbor search space |
k.anchor |
How many neighbors (k) to use when finding anchors |
k.filter |
How many neighbors (k) to use when filtering anchors. Set to NA to turn off filtering. |
k.score |
How many neighbors (k) to use when scoring anchors |
max.features |
The maximum number of features to use when specifying the neighborhood search space in the anchor filtering |
nn.method |
Method for nearest neighbor finding. Options include: rann, annoy |
n.trees |
More trees gives higher precision when using annoy approximate nearest neighbor search |
eps |
Error bound on the neighbor finding algorithm (from
|
approx.pca |
Use truncated singular value decomposition to approximate PCA |
mapping.score.k |
Compute and store nearest k query neighbors in the AnchorSet object that is returned. You can optionally set this if you plan on computing the mapping score and want to enable reuse of some downstream neighbor calculations to make the mapping score function more efficient. |
verbose |
Print progress bars and output |
Details
The main steps of this procedure are outlined below. For a more detailed description of the methodology, please see Stuart, Butler, et al Cell 2019. doi:10.1016/j.cell.2019.05.031; doi:10.1101/460147
Perform dimensional reduction. Exactly what is done here depends on the values set for the
reduction
andproject.query
parameters. Ifreduction = "pcaproject"
, a PCA is performed on either the reference (ifproject.query = FALSE
) or the query (ifproject.query = TRUE
), using thefeatures
specified. The data from the other dataset is then projected onto this learned PCA structure. Ifreduction = "cca"
, then CCA is performed on the reference and query for this dimensional reduction step. Ifreduction = "lsiproject"
, the stored LSI dimension reduction in the reference object is used to project the query dataset onto the reference. Ifl2.norm
is set toTRUE
, perform L2 normalization of the embedding vectors.Identify anchors between the reference and query - pairs of cells from each dataset that are contained within each other's neighborhoods (also known as mutual nearest neighbors).
Filter low confidence anchors to ensure anchors in the low dimension space are in broad agreement with the high dimensional measurements. This is done by looking at the neighbors of each query cell in the reference dataset using
max.features
to define this space. If the reference cell isn't found within the firstk.filter
neighbors, remove the anchor.Assign each remaining anchor a score. For each anchor cell, determine the nearest
k.score
anchors within its own dataset and within its pair's dataset. Based on these neighborhoods, construct an overall neighbor graph and then compute the shared neighbor overlap between anchor and query cells (analogous to an SNN graph). We use the 0.01 and 0.90 quantiles on these scores to dampen outlier effects and rescale to range between 0-1.
Value
Returns an AnchorSet
object that can be used as input to
TransferData
, IntegrateEmbeddings
and
MapQuery
. The dimension reduction used for finding anchors is
stored in the AnchorSet
object and can be used for computing anchor
weights in downstream functions. Note that only the requested dimensions are
stored in the dimension reduction object in the AnchorSet
. This means
that if dims=2:20
is used, for example, the dimension of the stored
reduction is 1:19
.
References
Stuart T, Butler A, et al. Comprehensive Integration of Single-Cell Data. Cell. 2019;177:1888-1902 doi:10.1016/j.cell.2019.05.031;
Examples
## Not run:
# to install the SeuratData package see https://github.com/satijalab/seurat-data
library(SeuratData)
data("pbmc3k")
# for demonstration, split the object into reference and query
pbmc.reference <- pbmc3k[, 1:1350]
pbmc.query <- pbmc3k[, 1351:2700]
# perform standard preprocessing on each object
pbmc.reference <- NormalizeData(pbmc.reference)
pbmc.reference <- FindVariableFeatures(pbmc.reference)
pbmc.reference <- ScaleData(pbmc.reference)
pbmc.query <- NormalizeData(pbmc.query)
pbmc.query <- FindVariableFeatures(pbmc.query)
pbmc.query <- ScaleData(pbmc.query)
# find anchors
anchors <- FindTransferAnchors(reference = pbmc.reference, query = pbmc.query)
# transfer labels
predictions <- TransferData(
anchorset = anchors,
refdata = pbmc.reference$seurat_annotations
)
pbmc.query <- AddMetaData(object = pbmc.query, metadata = predictions)
## End(Not run)