[R] sum two columns with same value

[Gabor Grothendieck]

Here are a few ways:


Here are a few ways:

# 1. using merge

m <- merge(snag_totale, log_totale, all = TRUE)
m[is.na(m)] <- 0
with(m, data.frame(AREA, sum = snag_ha + log_ha))

# 2. Use fact that AREA = 1:7 in log_totale
sum_totale <- log_totale; names(sum_totale)[2] <- "sum"
sum_totale$sum[snag_totale$AREA] <-
log_totale$log_ha[snag_totale$AREA] + snag_totale$snag_ha

# 3. using merge.zoo
# merge.zoo's fill=0 argument makes zero filling easier

library(zoo)

snag_zoo <- read.zoo(snag_totale)
log_zoo <- read.zoo(log_totale)

z <- merge(snag_zoo, log_zoo, all = TRUE, fill = 0)

# produce zoo object:
z$snag_zoo + z$log_zoo

# or produce data frame:
data.frame(AREA = time(z), sum = coredata(z$snag_zoo + z$log_zoo))


On Sat, Oct 17, 2009 at 3:36 AM, Alfredo Alessandrini
<alfreale74 at gmail.com> wrote:
> Hi,
>
> I've two dataframe:
>
>> snag_totale
>  AREA   snag_ha
> 1    2  1.628128
> 2    3 10.274249
> 3    4  2.778503
> 4    5 73.764307
> 5    7 12.015985
>> log_totale
>  AREA    log_ha
> 1    1  22.29846
> 2    2  17.16889
> 3    3  48.80377
> 4    4 144.18996
> 5    5  70.30962
> 6    6  61.81850
> 7    7  13.24876
>>
>
> How can I obtain a new data.frame, by the sum of value "snag_ha" +
> "log_ha" in the same "AREA"?
>
> Like this:
>
>   AREA       sum
> 1    1  22.29846
> 2    2  18.79702
> 3    3  59.07801
> 4    4 146.96847
> 5    5 144.07392
> 6    6  61.81850
> 7    7  25.26474
>
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