Hi,

I want to make a data frame which contains the positions of some searched values in another data frame.

Like:
Dataframe 1:

1  2  3  4  1  2  3  4
2  3  4  1  2  3  4  2
4  1  2  3  2  3  4  1

Let's say I searched on "4", then Dataframe 2 should contain:
x  y
1  4
1  8
2  3
2  7
3  1
3  7

I have written a routine, but it seems to me that it isn't that perfect:
x<- 0

y<- 0

for (j in 1:ncol(df)) {

for (i in 1:nrow(df)) {

if (df[i,j] == 3) {

x <- c(x,i)

y <- c(y,j)

}

}

}

df2 <- data.frame(x,y)

df2 <- df2[-1,]

Can someone come up with an elegant/faster solution, because the ultimate goal of this routine is to analyze an jpg image.

Kind regards

Bart
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