I'm trying to use SingleR to annotate UMAP plots in Seurat. I've been following this very helpful tutorial here (http://bioconductor.org/books/devel/SingleRBook/pancreas-case-study.html) and I see that SingleR can be used to annotate clusters in Scran but I haven't been able to figure out how to do the same thing in Seurat. Would someone be able to help me do it? I've pasted a portion of my code below to give a sense of what I want to achieve and what I have been trying.

```
library(Seurat)
library(DropletUtils)
library(SingleR)
library(celldex)

# Write seurat_integrated to 10X file
write10xCounts(x=seurat_integrated@assays$RNA@counts, path='seurat_integrated_10
X/')

# Annotate with SingleR
new.data <- Read10X("seurat_integrated_10X")
ref.data <- MouseRNAseqData()

predictions <- SingleR(test=new.data, assay.type.test="integrated",
                       ref=ref.data, labels=ref.data$label.main,
                       de.method="wilcox")
table(predictions$labels)

# Annotate UMAP clusters
seurat_integrated$celltypes <- predictions$pruned.labels
DimPlot(dummy_seurat_integrated, reduction="umap", split.by="celltypes")
```
I've had trouble pasting it in here but in the link, there is a SingleR-labelled TSNE plot achieved using Scran. I'm trying to do the same thing, but using Seurat.
Provide the `clusters` parameter to your `SingleR` call and basically proceed as you've shown. I'd recommend reading the `SingleR` function documentation, i.e. `?SingleR` from within R.