R: Mean subset sequence from dataframe - r

Question

I have been facing a problem for three days and I cannot get any answer about why it does not work. I have tried quite a lot different ways, but I am just going to post the one I believe is likely to be closest to the solution. I am going to put a reduce example about what I want to ask.
I have 7 csv files (called 001.csv, 002.csv, ... etc), in a folder called "Myfolder".
I have been trying to get a function that merged into an unique data.frame all this different .csv files using for-loop and r.bind and finally return the mean from either column "Colour1" or "Colour2" depending in the "colour" (column) and the "Children" (rows) I choose, and of course without missing values "Na". As an example when I merge the files I get a data frame like this data frame:
Colour1 Colour2 Children
NA NA 1
9 NA 2
NA NA 2
NA 5 3
7 NA 4
NA NA 5
NA 8 5
2 NA 6
6 3 6
14 NA 7
This is the the example of the function I want to build get_mean <- function(directory, colour, children)
What I have tried
get_mean <- function(directory, colour, children) {
files <- list.files(directory, full.names=TRUE)
allfiles <- data.frame()
for(i in 1:7) {
allfiles <- rbind(allfiles, read.csv(files[i]))
}
if(colour == "colour1"){
mean(allfiles$colour1[allfiles$Children == children], na.rm = TRUE)
}
if(colour == "colour2"){
mean(alllists$colour2[alllist$Children == children], na.rm = TRUE)
}
}
When I tried for example:
get_mean("Myfolder", "colour1", 3:6)
I get
In alllist$ID == id :
longer object length is not a multiple of shorter object length
and when I try:
get_mean("Myfolder", "colour1", 6)
I get:
>
Yes guys....I get back absolutely nothing.
What do you think guys? any correction to it? any other way to get the mean?
Note: all the data I put in here is not the one I am using. This is just an example from an exercise much bigger. I have tried to make a really small example with different names and numbers in order to don't discuss about the exercise itself and other could copy the solution

Answer 1

Here is a corrected and more readable version of your function - I named your data.frame all files df, I also added a check on colour:
get_mean <- function(directory, colour, children) {
files = list.files(directory, full.names=T)
df = do.call(rbind, lapply(files[1:7], read.csv))
# check the colour argument
if(!is.element(colour, c('colour1','colour2')))
stop(sprtinf('colour argument value %s is not part of df column', colour))
mean(df[[colour]][df$Children == children], na.rm=TRUE)
}