How to convert data frame in r from positive to negative

Question

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?

Solution 1

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

Solution 2

Here'a a tidyverse way to alter only the numeric columns.

library(dplyr)

df_neg <- df %>% 
  mutate_if(is.numeric, funs(. * -1))

Solution 3

This is working :

data$negative = data$positive*(-1)

Comments

[hpesoj626]

What is the output of df_neg?

[Melissa Key]

Does your data frame have any non-numeric values? (e.g. strings or factors)

[neilfws]

That code should work (even without the parentheses). What's the error?

[Niccola Tartaglia]

it was indeed the non-numerics

[thelatemail]

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