Using R package pheatmap to draw heatmaps. Is there a way to assign a color to NAs in the input matrix? It seems NA gets colored in white by default.
E.g.:

```
library(pheatmap)
m<- matrix(c(1:100), nrow= 10)
m[1,1]<- NA
m[10,10]<- NA
pheatmap(m, cluster_rows=FALSE, cluster_cols=FALSE)

```

Thanks