R: Add data from row to column with conditions
I have two data frames,
df1
number x_1 y_1
1 a a
2 a b
3 b b
4 c b
5 c c
df2
number_1 x_1 y_1 number_2 x_2 y_2
1 2
1 3
1 4
1 5
2 3
2 4
2 5
3 4
3 5
4 5
I want to add data to columns x_1, y_1, x_2, y_2 based on whether number_1 and number_2 match the numbers in number column in df1. So in the first two lines of df2, I must have:
df2
number_1 x_1 y_1 number_2 x_2 y_2
1 a a 2 a b
1 a a 3 b b
I've tried something like this but it doesn't work and it takes a very long time with an extremely huge dataset:
for(i in 1:nrow(df1))
for(j in 1:nrow(df2))
if(df2$number_1[j] == df1$number[i])
df2$x_1[j] = df1$x_1[i]
df2$y_1[j] = df1$y_1[i]
if(df2$number_2[j] == df1$number_1[i])
df2$x_1[j] = df1$x_1[i]
df2$y_1[j] = df$y_1[i]
I am a beginner, so I would really appreciate if you can explain the steps you are suggesting. Thank you very much.
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1 answer
Try either merge
or left_join
fromdplyr
merge(df1,
merge(df1,df2[,c(1,4)], by.x='number', by.y='number_1'),
by.x='number', by.y='number_2')
or
library(dplyr)
left_join(
left_join(df2[c(1,4)], df1, by=c('number_1'='number')) ,
df1, by=c('number_2'='number'))
Or, as @David Arenburg mentioned in the comments, match
can be used here.
df2[c("x_1", "y_1")] <- df1[match(df2$number_1, df1$number), 2:3]
df2[c("x_2", "y_2")] <- df1[match(df2$number_2, df1$number), 2:3]
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