R find maxima of multiple variables from multiple .CSV files - r

Question

I have multiple csv's, each containing multiple observations for one participant on several variables. Let's say each csv file looks something like the below, and the name of the file indicates the participant's ID:
data.frame(
happy = sample(1:20, 10),
sad = sample(1:20, 10),
angry = sample(1:20, 10)
)
I found some code in an excellent stackoverflow answer that allows me to access all files saved into a specific folder, calculate the sums of these emotions, and output them into a file:
# access all csv files in the working directory
fileNames <- Sys.glob("*.csv")
for (fileName in fileNames) {
# read original data:
sample <- read.csv(fileName,
header = TRUE,
sep = ",")
# create new data based on contents of original file:
data.summary <- data.frame(
File = fileName,
happy.sum = sum(sample$happy),
sad.sum = sum(sample$sad),
angry.sum = sum(sample$angry))
# write new data to separate file:
write.table(data.summary,
"sample-allSamples.csv",
append = TRUE,
sep = ",",
row.names = FALSE,
col.names = FALSE)}
However, I can ONLY get "sum" to work in this function. I would like to not only find the sums of each emotion for each participant, but also the maximum value of each.
When I try to modify the above:
for (fileName in fileNames) {
# read original data:
sample <- read.csv(fileName,
header = TRUE,
sep = ",")
# create new data based on contents of original file:
data.summary <- data.frame(
File = fileName,
happy.sum = sum(sample$happy),
happy.max = max(sample$happy),
sad.sum = sum(sample$sad),
angry.sum = sum(sample$angry))
# write new data to separate file:
write.table(data.summary,
"sample-allSamples.csv",
append = TRUE,
sep = ",",
row.names = FALSE,
col.names = FALSE)}
I get the following warning message:
In max(sample$happy) : no non-missing arguments to max; returning -Inf
Would sincerely appreciate any advice anyone can give me!

Answer 1

using your test data, the max() statement works fine for me. Is it related to a discrepancy between the sample code you have posted and your actual csv file structure?