I would like to multiply my r dataframe with minus 1, in order to reverse the signs of all values (turn + to - and vice versa):
This does not work:
df_neg <- df*(-1)
Is there another way to do this?
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What is the output of `df_neg`? – hpesoj626 May 01 '18 at 03:56
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2Does your data frame have any non-numeric values? (e.g. strings or factors) – Melissa Key May 01 '18 at 03:57
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That code should work (even without the parentheses). What's the error? – neilfws May 01 '18 at 03:58
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it was indeed the non-numerics – Niccola Tartaglia May 01 '18 at 04:11
3 Answers
10
Here'a a tidyverse way to alter only the numeric columns.
library(dplyr)
df_neg <- df %>%
mutate_if(is.numeric, funs(. * -1))
neilfws
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Assuming your data frame is all numeric, the code you posted should work. I'm going to assume you have some non-numeric values we need to work around
# make a fresh copy
df_neg <- df
# now only apply this to the numeric values
df_neg[sapply(df_neg, is.numeric)] <- df_neg[sapply(df_neg, is.numeric)] * -1
Melissa Key
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Looks like the right strategy to me. You can also save off `sel <- sapply(df_neg, is.numeric)` first so you don't have to type it all out twice. E.g.: `df_neg[sel] <- df_neg[sel] * -1` – thelatemail May 01 '18 at 05:04
