Compare first element of a list with another list

Question

I am using R and need a hint to solve my problem:

I have two lists and I want to compare the values of the first row of list "a" with the values of the first row of list "b". If the element exists, I want to write the value of the second row of list "b" into the second row of list "a".

So, here is list "a":

X.WORD    FREQ
abase     0
abased    0
abasing   0
abashs    0

here list "b"

V1        V2
arthur    11
abased    29
turtle    9
abash     2

The result should be

X.WORD    FREQ
abase     0
abased    29
abasing   0
abashs    0

Thanks for your answers

What if "abased" was in row 3 of your "list b"? Perhaps you are just looking for a `merge()`.. — talat, Nov 03 '14 at 15:22
And I think you mean "column" instead of "row". Your data has two columns, lots of rows. — Spacedman, Nov 03 '14 at 15:46
possible duplicate of [How to join data frames in R (inner, outer, left, right)?](http://stackoverflow.com/questions/1299871/how-to-join-data-frames-in-r-inner-outer-left-right) — talat, Nov 03 '14 at 16:00

David Arenburg · Accepted Answer · 2014-11-03T15:58:10.090

That's just a task for simple merge in base R

Res <- merge(a, b, by.x = "X.WORD", by.y = "V1", all.x = TRUE)[, -2]
Res$V2[is.na(Res$V2)] <- 0
Res
#    X.WORD V2
# 1   abase  0
# 2  abased 29
# 3  abashs  0
# 4 abasing  0

Data

a <- structure(list(X.WORD = structure(c(1L, 2L, 4L, 3L), .Label = c("abase", 
"abased", "abashs", "abasing"), class = "factor"), FREQ = c(0L, 
0L, 0L, 0L)), .Names = c("X.WORD", "FREQ"), class = "data.frame", row.names = c(NA, 
-4L))

b <- structure(list(V1 = structure(c(3L, 1L, 4L, 2L), .Label = c("abased", 
"abash", "arthur", "turtle"), class = "factor"), V2 = c(11L, 
29L, 9L, 2L)), .Names = c("V1", "V2"), class = "data.frame", row.names = c(NA, 
-4L))

score 1 · Answer 2 · answered Nov 03 '14 at 15:36

Here is one approach.

library(dplyr)

ana <- foo %>%
    left_join(foo2, by = c("X.WORD" = "V1")) %>%
    select(-FREQ) %>%
    rename(FREQ = V2)

ana$FREQ[is.na(ana$FREQ)] <- 0

#   X.WORD FREQ
#1   abase    0
#2  abased   29
#3 abasing    0
#4  abashs    0

Data

foo <- structure(list(X.WORD = structure(c(1L, 2L, 4L, 3L), .Label = c("abase", 
"abased", "abashs", "abasing"), class = "factor"), FREQ = c(0L, 
0L, 0L, 0L)), .Names = c("X.WORD", "FREQ"), class = "data.frame", row.names = c(NA, 
-4L))

foo2 <- structure(list(V1 = structure(c(3L, 1L, 4L, 2L), .Label = c("abased", 
"abash", "arthur", "turtle"), class = "factor"), V2 = c(11L, 
29L, 9L, 2L)), .Names = c("V1", "V2"), class = "data.frame", row.names = c(NA, 
-4L))

I get the following error message: Error: cannot join on columns 'V1' x 'X.WORD' : index out of bounds — Roger Sánchez, Nov 03 '14 at 15:52
@RogerSánchezNa Thanks for your message. I tested the code with the data. It is running on my machine. Could you double check it? — jazzurro, Nov 03 '14 at 16:22

Compare first element of a list with another list

2 Answers2