R - Using column value in data frame to lookup matrix name and summarize matrix

Question

I am trying to add a new column to an existing data frame which shows the number of one's in a binary matrix. One column in the existing data frame has the the matrix names whose count/sum I am trying to find.

For example,

r <- 10

c <- 10

MatA <- matrix(sample(0:1,r*c, replace=TRUE),r,c)

MatB <- matrix(sample(0:1,r*c, replace=TRUE),r,c)

MatC <- matrix(sample(0:1,r*c, replace=TRUE),r,c)



mat <- c("MatA","MatB","MatC")

size <- c(4,6,10)

df <- data.frame(mat,size)

I need to lookup the

mat

column values such as

MatA, MatB, MatC

from

df

dataframe to match the matrix names

MatA, MatB, MatC

and return the number of 1's in each of the binary matrix added to the

df

dataframe in a new column.

I tried using loops, apply functions but am lost at how to use the column values

MatA

from

df$mat

as a lookup for matrix name

MatA

and return

sum(MatA==1)

to new column in dataframe

df

.

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Answer 1

Use get to reference variable by string

set.seed(7)
df$binary <- lapply(mat, function(x) sum(get(x)))

To use the data.frame column if stored as factors

df$binary <- lapply(levels(df$mat)[df$mat], function(x) sum(get(x)))

To store column as strings and not factors

df <- data.frame(mat, size, stringsAsFactors = FALSE)
df$binary <- lapply(df$mat, function(x) sum(get(x)))

> df
   mat size binary
1 MatA    4     47
2 MatB    6     58
3 MatC   10     54

R - Using column value in data frame to lookup matrix name and summarize matrix

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