Help for R -- Error in FUN(X[[i]], ...) : object 'descr' not found

[gsebehat]

Hello,

I am working on my project in RStudio using Rmarkdown and I got the following error:
Error in FUN(X[[i]], ...) : object 'descr' not found
A due date will be today. Please help!
Here is the code:

# First save the results
dataset_stats_by_Grade <- by(data = dataset, INDICES = dataset$Grade, 
                    FUN = descr, stats = c("mean", "sd", "min", "med", "max"),transpose = TRUE)

# Then use view(), like so:
View(dataset_stats_by_Grade, method = "pander", style = "rmarkdown")
When I run, I found the following error:
Error in FUN(X[[i]], ...) : object 'descr' not found 

Thanks!!