CODEWITHSUNDEEP
r
JohnK
JohnK

Reputation: 1039

Expand grid with an ordered pair and a third variable in R

I have been trying to generate all combinations of an ordered pair of variables with a third variable, that is combine every pair (z1, z2) below with all z3.

theta <- seq(0, 2*pi, length = 5) 
z1 <- cos(theta) ;z2 <- sin(theta)
z3 <- seq(-3, 3, length = 5)

I would normally use the expand.grid function but here this is not appropriate as it will generate combinations of the three variables destroying the ordering. I was wondering, is there a function in R that can do this? All help is greatly appreciated, thank you.

Upvotes: 3

Views: 662

Answers (2)

Steven Beaupr&#233;
Steven Beaupr&#233;

Reputation: 21621

Another alternative:

library(tidyr)
df <- data.frame(z1, z2, z3)
expand(df, nesting(z1, z2), z3)

Upvotes: 6

akrun
akrun

Reputation: 887118

We paste the 'z1' and 'z2' and do the expand.grid with 'z3'. From the output ('d1'), we split the 'Var1' i.e. the pasted vectors into two columns.

d1 <- expand.grid(paste(z1,z2), z3)
transform(read.table(text=as.character(d1$Var1), header=FALSE), V3= d1$Var2)

Upvotes: 1

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