尝试将多个 jpeg 写入 r 中的文件时出错

Question

I have over 600 WAV files I am trying to plot and write to a file. I made a loop to do this, but it gives an error that says "Error in audiomoth13_allfiles@left: trying to get slot "left" from an object of a basic class ("list") with no slots"

Below is my code that produces the error.

for (audiomoth13wavfiles in seq_along(audiomoth13_allfiles)) {
audiomoth13_allfiles<-lapply(audiomoth13wavfiles,readWave)
snd<-audiomoth13_allfiles@left 
fs<-audiomoth13_allfiles@samp.rate
dur<-length(snd)/audiomoth13_allfiles@samp.rate
snd<-snd-mean(snd)
timearray<-(0:(5760000-1))/audiomoth13_allfiles@samp.rate
jpeg(file= paste0("C:/ACLF_Audiomoth_13/ACLF_Audiomoth_13/plots",names(audiomoth13wavfiles) 
[audiomoth13wavfiles],".jpeg"))
plot(timearray,snd,type='l',xlab='Time',ylab='Amplitude')
dev.off()} 

The error occurs whether or not I put audiomoth13_allfiles<-lapply(audiomoth13wavfiles,readWave) in the loop. audiomoth13_allfiles contains all the files as an S4 object with slots

Is there another way to do this? Thanks.

Answer 1

You are conflating a for loop with lapply , which is sort of redundant. Try something akin to what is shown below (or use a for loop instead of lapply ). The idea is to loop through the indices of all.wav files. This way you can use the same index for the file name and the file read in using readWave .

library(tuneR)
wavfiles <- list.files(pattern="*.wav")
lapply(seq_along(wavfiles), function(x){
    wav <- readWave(wavfiles[x])
    snd <- wav@left
    fs <- wav@samp.rate
    dur <- length(snd)/fs
    snd <- snd - mean(snd)
    timearray <- seq(0, dur, length.out=length(snd))
    jpeg(file=paste0(tools::file_path_sans_ext(wavfiles[x]), "_plot.jpg"))
        plot(snd~timearray, type='l', xlab='Time', ylab='Amplitude')
    dev.off()}
)