R extract value from a data frame with different length based on a column

Question

I have 2 data frames.

Data1 is like this (with length of 50)

|Depth|Age|
|1|56|
|2|78|
|3|104|
|4|157|
|5|200|

Data 2 is like this (with lenght of 300)

|Age|Rate|
|1|15.2|
|2|15.4|
|3|15.6|
|4|16.4|
|5|17.8|
|..|..|
|300|19.1|

I want to create a new column Rate in Data1 based on Age, and the value of Rate is from Data2 with corresponding Age (same age in Data1 and Data2).

I want the output to be like this:

|Depth|Age|Rate|
|1|56|18.1|
|2|78|20.1|
|3|104|21.0|
|4|157|20.2|
|5|200|23.1|

I tried if else and it said cannot work because the data frame's length is different.

Is there any way to do this?

`merge(df1, df2, by = 'Age', all.x = TRUE)` is what you need — Onyambu, Apr 22 '22 at 21:41
The merge(df1, df2) worked! I feel dumb, such a simple solution! thank you so much!!!!!! — monruw, Apr 22 '22 at 21:51
Be sure to always [research](https://meta.stackoverflow.com/questions/261592/how-much-research-effort-is-expected-of-stack-overflow-users) before asking. — Parfait, Apr 23 '22 at 16:34

score 0 · Answer 1 · edited Apr 23 '22 at 00:38

0

Found it using match:

data1$rate <- data2$rate[match(data1$age,data2$age)]

I found the solution here Add column to data frame based on values of another column in another row

edited Apr 23 '22 at 00:38

Jeremy Caney

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answered Apr 22 '22 at 21:48

monruw

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R extract value from a data frame with different length based on a column

1 Answers1