Seurat error: error in evaluating the argument 'x' in selecting a method for function 'colSums': invalid character indexing"

library(dplyr)
library(Seurat)
library(patchwork)

 hvc.data <- readRDS(file = "E:\\Nikhil Sampath\\HVCcounts_forNS.RDS")                      

 hvc <- CreateSeuratObject(counts = hvc.data, project = "hvc stuff", min.cells = 3, min.features = 200)

Mito_genes <- 
  c(
    "ATP6",
    "ATP8",
    "COX1",
    "COX2",
    "COX3",
    "CYTB",
    "ND1",
    "ND2",
    "ND3",
    "ND4",
    "ND4L",
    "ND5",
    "ND6"
  )
 
 
hvc[["percent.mito"]] <-
   PercentageFeatureSet(
     hvc,
     features = Mito_genes
   )
 
 

I'm working through the tutorial for Seurat 4.3.0, and I'm having an issue with the PercentageFeatureSet command.

I am basically trying to use PercentageFeatureSet() to look through an assay and add a column indicating the percentage of mitochondrial rna present within the sample data. I was initially running Seurat 5.0, so i reinstalled to 4.3.0, and that didn't help. I've tried using GetAssayData() to pull the assay data straight from the initial RDS file, and then using that to create a Suerat object, but I got the same error. Sorry if any of my lanugage is incorrect, this is my first day using the library.

One likely explanation is that your gene names in the data are not the same format as the gene names you're defining in Mito_genes. For example, that would be the case if your data was generated using ENSEMBL gene IDs (ENSG000xxx).

To determine that, try looking at some gene IDs in your data, with:

head(rownames(GetAssayData(hvc)))