Error in FUN(left, right) : non-numeric argument to binary operator-CodePudding

i'm trying to add values to each individual columns in a specific rows which i'm using a loop but it keeps giving the error of "non-numeric argument to binary operator" so maybe i am thinking the program reads the index value of the column?

This is my code:

col1st <- colnames(NB1stRow)[5:74]
for(i in seq_along(col1st)){
  NB1stRow[i] <- NB1stRow[i]*2
}

Here's how a column would look like

NB1stRow[6]
   X417.897
1  21.29759
2  22.52447
3  25.59260
4  29.67289
5  34.45366
6  30.30945
7  28.02665
8  28.13356
9  31.67405
10 28.65952
11 28.49534
12 32.18732
13 35.24368
14 32.02267
15 30.92876

I am using base R.

CodePudding user response：

For example,

dummy <- matrix(c(1:25), nrow = 5, byrow = TRUE) %>% as.data.frame()
  V1 V2 V3 V4 V5
1  1  2  3  4  5
2  6  7  8  9 10
3 11 12 13 14 15
4 16 17 18 19 20
5 21 22 23 24 25

with this data, it will work.

for (i in seq_along(colnames(dummy))){
  dummy[i] <- dummy[i]*2
}
  V1 V2 V3 V4 V5
1  2  4  6  8 10
2 12 14 16 18 20
3 22 24 26 28 30
4 32 34 36 38 40
5 42 44 46 48 50

when change one values into text, like

dummy <- matrix(c(1:25), nrow = 5, byrow = TRUE) %>% as.data.frame()
dummy[3,4] <- "a"
  V1 V2 V3 V4 V5
1  1  2  3  4  5
2  6  7  8  9 10
3 11 12 13  a 15
4 16 17 18 19 20
5 21 22 23 24 25

for (i in seq_along(colnames(dummy))){
  dummy[i] <- dummy[i]*2
}

Error in FUN(left, right) : non-numeric argument to binary operator

try check str(NB1stRow[,c(5:74)]) have any chr or factor or etc

CodePudding user response：

First check if the class of the data is numeric. str(NB1stRow) will show you classes of each column. If they are not numeric, turn them to numeric by -

cols <- 5:74
NB1stRow[cols] <- lapply(NB1stRow[cols], as.numeric)

Multiplication (*) doesn't require loop and it can be applied to dataframe directly so you can do

NB1stRow[cols] <- NB1stRow[cols] * 2

CodePudding user response：

Assuming that columns 5:74 are numeric, the problem is that seq_along(col1st) is 1:70 so it is trying to double those columns, not columns 5:74. Using DF to represent the data frame we want:

ix <- 5:74
for(i in ix) DF[i] <- 2 * DF[i]

or just

DF[ix] <- 2 * DF[ix]