Hello,
Use expand.grid.
One line at a time, to make it clearer:
a <- 1:5
b <- 1:10
m <- expand.grid(b, a)[, c(2, 1)]
resu <- matrix(NA, nrow=5, ncol=10)
for (i in 1:5)
{
for (j in 1:10) # --------------> was 1:5 in your post
{
resu[i,j]=a[i]+b[j] # will be more complicated
}
}
f <- function(i, j) a[i] + b[j]
mat <- expand.grid(a, b)
res2 <- apply(mat, 1, function(ii) f(ii[1], ii[2]))
res2 <- matrix(res2, nrow = 5)
identical(resu, res2) # TRUE
Hope this helps,
Rui Barradas
Em 06-09-2012 15:50, Jie escreveu:
Dear All,
Suppose I have two loops and would like to convert it to sapply, how
to achive the goal?
Below is an example, the calculation inside the loop is not essential,
so please do not use tricks for this part.
a <- 1:5
b <- 1:10
resu <- matrix(NA,nrow=5,ncol=10)
for (i in 1:5)
{
for (j in 1:5)
{
resu[i,j]=a[i]+b[j] # will be more complicated
}
}
# Do I have to create a list like this i order to use sapply?
data=list()
for (i in 1:5)
{
for (j in 1:5)
{
data[[(i-1)*5+j]]=list(a=a[i],b=b[j])
}
}
Thank you for your attention.
Best wishes,
Jie
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and provide commented, minimal, self-contained, reproducible code.
