R error message when using t()%*% "requires numeric/complex matrix/vector arguments"

Question

I am working on a social network analysis assignment where I need to create a network from a matrix. I’m trying to create a matrix which shows what students are linked by classes they have in common, or not (a person-person matrix). I have wrangled the original data into the first iteration of a matrix and now want to multiply the matrix. My dataset and current matrix is a bigger version of the below:

names <- c("Tom", "Dick", "And", "Harry")
class <- c("cs1", "cs2", "cs3", "cs1")
count <- c(1, 1, 0, 1)
df = data.frame (names, class, count)
df2 <- spread(df, "class", "count")

When I run the matrix multiplication code I get this error message: Error in t(m) %*% m : requires numeric/complex matrix/vector arguments.

m <- as.matrix(df2)
m2 <- t(m) %*% m

A previous SO question and answer Matrix multiplication in R: requires numeric/complex matrix/vector arguments suggested the matrix needed to contain numeric or factor values, so I added the below code but I got the same the error message:

df2 %>% mutate_if(is.factor, as.character) -> df2
m <- as.matrix(df2)
m2 <- t(m) %*% m

If anyone can help me understand where I’m going wrong/ what the error message means here, I would appreciate it. Thank you!

P.S. Sorry for ugly code…new to R.

AidanGawronski AidanGawronski · Accepted Answer · 2017-12-14T01:29:12

This might help:

# fill NA with 0
df2[is.na(df2)] <- 0

# make row names the names of the people
row.names(df2) <- df2$names
df2 <- df2[,-1]

m <- as.matrix(df2)
m2 <- t(m) %*% m

R error message when using t()%*% "requires numeric/complex matrix/vector arguments"

1 Answers