One line of R shiny app not working as expected

[Saurish_Seksaria]

I have the following line in my code:

matching_row_index <- which(apply(df1, 1, identical, row_df))

Here, row_df is a dataframe with only one row. df1 is another dataframe with many rows and exact same columns as row_df. I wish to find the index of that row in df1, which matches with the single row of row_df. This value of the index is to be given to matching_row_index. However, on running the code and using print statements, print(matching_row_index) gives output integer(0). Also other functionality in the app which depends on mathing_row_index is not working as expected. print(row_df) gave correct output as expected, so apparently row_df is fine.

Can someone please correct this line of code or explain what is causing the bug?

[scottyd22]

Hi @Saurish_Seksaria. I'm not exactly sure why your example fails, but below is an example that gets at the desired outcome in a slightly different way. I wrote a small function that checks for matching rows using the identical() function as you proposed, then step through each row of df1 using lapply().

# function to check rows for a match
check_rows = function(i, mydata, myrow) {
  identical(mydata[i,], myrow)
}

df1 = mtcars

# example trying to match the 7th row
row_df = mtcars[7,]
matching_row_index = which(lapply(1:nrow(df1), check_rows, df1, row_df) == T)
matching_row_index
#> [1] 7

# example trying to match the 23rd row
row_df = mtcars[23,]
matching_row_index = which(lapply(1:nrow(df1), check_rows, df1, row_df) == T)
matching_row_index
#> [1] 23

Created on 2023-09-25 with reprex v2.0.2.9000

[nirgrahamuk]

it may be natural to use slider

df1 = mtcars
row_df = mtcars[7,]

library(slider)
which(slide_lgl(df1,
                \(x)identical(x,row_df)))

# Duster 360 
#         7

[Saurish_Seksaria]

Thanks for the help. I'll try this out

[Saurish_Seksaria]

Thanks for the help. I'll try this out too