I have data frame with the first column as a categorical identifier, the second column as a frequency value and the remaining columns as raw data counts. I want to multiply all the count columns by the frequency column but not the first two.
All the raw count columns start with a capital letter followed by a full stop, e.g "L.abd", T.xyz etc.
For example, if I use the code:
require(dplyr)
ID <- c(1,2,3,4,5,6)
Freq <- c(0.1,0.2,0.3,0.5,0.1,0.3)
L.abc <- c(1,1,1,3,1,0)
L.ABC <- c(0,3,2,4,1,1)
T.xyz <- c(1,1,1,1,0,1)
F.ABC <- c(4,5,6,5,3,1)
df <- as.data.frame(cbind(ID, Freq, L.abc, L.ABC, T.xyz, F.ABC))
df_new <- df %>% mutate_each(funs(.*Freq), starts_with("L."))
I can create a new data frame containing the categorical data columns along with those columns starting with "L." which have been multiplied by the corresponding frequency value.
Is there a way to change the "starts_with" command to select all columns that begin with a capital letter and a full stop? My attempts to date using modifications such as "[A-Z]." have been unsuccessful.
Thanks in advance
For these cases, matches
would be more appropriate
df %>%
mutate_each(funs(.*Freq), matches("^[A-Z]\\.", ignore.case=FALSE))
Here, I am assuming that you wanted to select
only column names that start with a capital letter (^[A-Z]
) followed by a .
. We have to escape the .
(\\.
), otherwise it will be considered as any single character.
I am not changing anything except in the starts_with
part. In the mutate_each
if we need to pass a function, it can be passed inside a funs
call. In the above code, we are multiplying each of the columns (.
) selected by the matches
with the 'Freq' column.
According to ?select
‘matches(x, ignore.case = TRUE)’: selects all variables whose name matches the regular expression ‘x’
EDIT: Added @docendodiscimus comment's
I just answered a related question from other user, mutate_each
will be deprecated in favor of mutate_at
.
In your case the equivalent code is:
df %>% mutate_at(.cols=vars(matches("^[A-Z]\\.", ignore.case=FALSE)), .funs=funs(.*Freq))
ID Freq L.abc L.ABC T.xyz F.ABC
1 1 0.1 0.1 0.0 0.1 0.4
2 2 0.2 0.2 0.6 0.2 1.0
3 3 0.3 0.3 0.6 0.3 1.8
4 4 0.5 1.5 2.0 0.5 2.5
5 5 0.1 0.1 0.1 0.0 0.3
6 6 0.3 0.0 0.3 0.3 0.3
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