[R] how to add two data.frame with the same column but different row numbers

[Dennis Murphy]

Hi:

Here's one approach:

> df1 <- data.frame(x = letters[1:3], y = 1:3)
> df2 <- data.frame(x = c('a', 'c'), z = c(6, 1))
> dfm <- merge(df1, df2, all.x = TRUE)
> dfm
  x y  z
1 a 1  6
2 b 2 NA
3 c 3  1
sumdf <- data.frame(x = dfm$x, y = rowSums(dfm[, -1], na.rm = TRUE))
  x y
1 a 7
2 b 2
3 c 4

HTH,
Dennis

On Fri, Apr 15, 2011 at 1:31 PM, zhenjiang xu <zhenjiang.xu at gmail.com> wrote:
> Hi all,
>
> Suppose I have 2 data.frame , a and b, how can I add them together to get c?
> Thanks
>> a
>  A
> a 1
> b 2
> c 3
>
>> b
>  A
> a 6
> c 1
>
>> c
>   A
> a 7
> b 2
> c 4
>
> --
> Best,
> Zhenjiang
>
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>
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