pivot_longer with names_pattern [duplicate] - r

Question

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How to use Pivot_longer to reshape from wide-type data to long-type data with multiple variables
(1 answer)
Closed 1 year ago.
I am quite new to the whole programing stuff, but i need to skript reproducable for large datasets. I hope I provided a sufficient example.
I have a dataframe like this (with 8 more "Nutrients" and 5 more "trade-elements" and much more Years):
Year<-c(1961,1962)
Total_Energy_kcal_Production<-c(5,8)
Total_Energy_kcal_Import<-c(6,1)
Total_Ca_g_Production<-c(3,4)
Total_Ca_g_Import<-c(3,8)
df<-cbind(Year,Total_Energy_kcal_Production, Total_Energy_kcal_Import, Total_Ca_g_Production, Total_Ca_g_Import)
looks like:
Year Total_Energy_kcal_Production Total_Energy_kcal_Import Total_Ca_g_Production Total_Ca_g_Import
1961 5 6 3 3
1962 8 1 4 8
and I want it to look like this:
Year Nutrient Production Import
1961 Total_Energy_kcal 5 6
1962 Total_Energy_kcal 8 1
1961 Total_Ca_g 3 3
1962 Total_Ca_g 4 8
I tried a lot with pivot_longer and names_patern. I thought this would work, but I do not fully understand the arguments:
df_piv<-df%>%
pivot_longer(cols = -Year, names_to = "Nutrient",
names_pattern = ".*(?=_)")
I get an error-message that i can not interprete:
Error: Can't select within an unnamed vector.

Answer 1

You can provide names_pattern regex as :
tidyr::pivot_longer(df,
cols = -Year,
names_to = c('Nutrient', '.value'),
names_pattern = '(.*)_(\\w+)')
# Year Nutrient Production Import
# <dbl> <chr> <dbl> <dbl>
#1 1961 Total_Energy_kcal 5 6
#2 1961 Total_Ca_g 3 3
#3 1962 Total_Energy_kcal 8 1
#4 1962 Total_Ca_g 4 8
This will put everything until the last underscore in Nutrient column and the remaining data is kept as column name.
data
cbind will create a matrix, use data.frame to create data.
df<-data.frame(Year,Total_Energy_kcal_Production,Total_Energy_kcal_Import,
Total_Ca_g_Production, Total_Ca_g_Import)