FeaturePlot from Seurat: change its title FeaturePlot is a function in Seurat package.

And in the vignette it is written that if we specify parameter do.return = TRUE it should return ggplot2 object. It is not working. My goal here is just to change the title of the plot. In case of violin plot I can do the following:

VlnPlot(object = seurat_object, features.plot = id, do.return = TRUE) + labs(title = endothelial_symbols[1])


But with FeaturePlot similar code fails to work:

FeaturePlot(object = seurat_object, features.plot = id, cols.use = c("grey", "blue"),
                          reduction.use = "tsne", do.return = TRUE) + labs(title = endothelial_symbols[1])


Giving the error:


  Error in FeaturePlot(object = seurat_object, features.plot = id, cols.use = c("grey",  : 
    non-numeric argument to binary operator


Any suggestions would be greatly appreciated.
I tried with some data that I have and this is working for me: 

p &lt;- FeaturePlot(object = seurat_object, features.plot = id, cols.use = c("grey", "blue"),
                      reduction.use = "tsne", do.return = TRUE)


lapply(p, function(x){x + labs(title = endothelial_symbols[1])})


I think it is because FeaturePlot returns several ggplot objects according to the ids you put. This is returned as a list of plots so you have to iterate each one for labeling.