How to compare each value at the same position from multiple datasets in R

Question

Suppose I have three datasets which have the same form.

set.seed(1)
df1<-as.data.frame(matrix(sample(c(1:4),15,replace=T),nrow=5))
set.seed(2)
df2<-as.data.frame(matrix(sample(c(1:4),15,replace=T),nrow=5))
set.seed(3)
df3<-as.data.frame(matrix(sample(c(1:4),15,replace=T),nrow=5))

df1              df2               df3
  V1 V2 V3         V1 V2 V3          V1 V2 V3
1  2  4  1       1  1  4  3        1  1  3  3
2  2  4  1       2  3  1  1        2  4  1  3
3  3  3  3       3  3  4  4        3  2  2  3
4  4  3  2       4  1  2  1        4  2  3  3
5  1  1  4       5  4  3  2        4  3  3  4

What I wanted to do is to assign a value of 1 to the case that at least one of the three values in the same position from the three datasets is greater than 3, otherwise 0. The output I expect would be

Merging the three datasets into one might be a solution. But, because my data is very huge, I doubt that way is a good idea. Any suggestion would be appreciated!

You really need to add `set.seed` here because `sample` return a different result each time. — David Arenburg, Sep 20 '15 at 09:34
@DavidArenburg Did you mean I need to use set.seed when I created the random matrices? — Shinzi Katoh, Sep 20 '15 at 09:40
Yes. You need to do something like `set.seed(123)` and then create the data frames and then show their values. Other wise we can't reproduce your data sets. — David Arenburg, Sep 20 '15 at 09:40
@DavidArenburg Oh. I see. I didn't know that point. Thanks for letting me know! :-) — Shinzi Katoh, Sep 20 '15 at 09:43

David Arenburg · Accepted Answer · 2015-09-20T10:19:35.787

4

Here's a possible solution that will save you merging the data sets

(((df1 > 3L) + (df2 > 3L) + (df3 > 3L)) > 0L) + 0L
#      V1 V2 V3
# [1,]  0  1  0
# [2,]  1  1  0
# [3,]  0  1  1
# [4,]  1  0  0
# [5,]  1  0  1

Or similarly

(Reduce(`+`, list(df1 > 3L, df2 > 3L, df3 > 3L)) > 0L) + 0L

The idea here is to check each value in each data set if it greater than 3, then sum up the TRUE results, check if the sum is > 0 and convert to integers by adding 0. This works because + and > are generic functions which have a data.frame method which preserves the dimensions of the data set, see ?Ops and more specifically methods(Ops).

edited Sep 20 '15 at 10:19

answered Sep 20 '15 at 09:36

David Arenburg

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Thanks much David. A quick question is what the 'L' followed by the number means? (I added set.seed with your advice. Thanks!) – Shinzi Katoh Sep 20 '15 at 09:56
The `L` is not necessary I'm just adding it by habit. Also, see my edit , I've mistakenly used `==` instead of `>` – David Arenburg Sep 20 '15 at 09:58
1

David. You saved me. It gave the perfect results. Thanks much for this help!! – Shinzi Katoh Sep 20 '15 at 10:04

How to compare each value at the same position from multiple datasets in R

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