RStudio: For-Loop with xtabs-CodePudding

Pretty simple: I'm trying to create a sequence of crosstabs. I thought all I needed was a for-loop and xtabs, but that hasn't worked out.

Say I have dataframe df, a list of column names list1 and a second list list2. I have written the following loop:

for (i in list1) {  
    for (j in list2) {  
    print(prop.table(xtabs(~i j,data=df),margin=2))} 
    }

However, when I run the loops, R spits out the following:

i1 j1 1
i1 j2 1
i1 j3 1
...

Why is this happening? If I write a standalone

prop.table(xtabs(~i j,data=df),margin=2)

with a certain i and j, I receive the table I'm looking for. Why does it break when I try to iterate the process?

CodePudding user response：

It sounds like you have i and j as character values from list1 and list2. If that is true, you will need to build your formula from those values, such as with as.formula or reformulate. You can use paste to put together the formula so identical to what you have with your example.

for (i in list1) {  
  for (j in list2) {  
    print(prop.table(xtabs(formula = as.formula(paste("~", i, " ", j)), data = df), margin = 2))
  } 
}

Or alternatively can use in your loop:

print(prop.table(xtabs(formula = reformulate(c(i, j)), data = cgd), margin = 2))