在 R 中查找和替换某些值

Question

I know that this has been asked thousand times already but the answers don't work for me.

I have a big dataset and need R to automatically seek and replace certain values in certain columns for me.

I tried this:

df$column <- replace (df$column, df$column, old number==new number)

for me it would look like this:

df$qual_a_a_s1m1a <- replace(df$qual_a_a_s1m1a, df$qual_a_a_s1m1a, 2==3)

If I get this to work, I could then build this for all columns and all values.

Can you explain why it doesn't work? Thanks and have a nice sunday:)

EDIT: This is one of the results I get:

replace(df$qual_a_a_s1m1a, df$qual_a_a_s1m1a, 6==1)

  [1]  0  0 NA  6 NA  0 NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA  2 NA
 [32] NA NA NA NA  1 NA NA NA NA NA NA NA NA  6 NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA
 [63] NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA
 [94] NA NA NA NA NA NA NA NA  6 NA NA NA NA NA NA

Instead of replacing the sixes with ones it put two zeroes in there at the first two positions.

Answer 1

Hi I think you have the syntax in the wrong format.... should it not be df$qual_a_a_s1m1a <- replace(df$qual_a_a_s1m1a, df$qual_a_a_s1m1a=3, 2)

also maybe you could use ifelse? not sure if it is faster or not but it is what I use a lot. Cheers

Answer 2

The syntax for replace is in the wrong format. See ?replace Your x is correct, but the list should be a list of your row numbers that you want to replace. Then vaules would be a list of the values you want the rows in list to be converted to.

This code will work a lot better than using replace():

# create fake data
df <- data.frame(qual_a_a_s1m1a=rep(1:3,times=3))
df

# let's change all the 2s to 3s
df$qual_a_a_s1m1a[df$qual_a_a_s1m1a==2] <- 3

df # all the 2s are now 3s