# [R] Extracting arithmetic mean for specific values from multiple .txt-files

Mon Jul 9 20:44:05 CEST 2012

```Hello,

There must be a difference in the file you are processing and in the one
excel and I are:

> fun <- function(x){
+ dat[ , 8] <- as.numeric(gsub("\\.", "", dat[, 8]))
+ mean(dat[, 8])
+ }
>
> sapply(list.files(pattern="XYZ.*\\.txt"), fun)
XYZ_34.txt
345210.4

This result is even better, more accurate than excel's.

AS for the second question, because with the dots, those values are read
by R as character and when put into the data.frame converted to factors,
the name R gives to categorical variables. You can see this with the

print(str(dat))
> str(dat)
'data.frame':   151 obs. of  8 variables:
\$ V1: int  2 2 2 2 2 2 2 2 2 2 ...
\$ V2: int  1 2 3 4 5 6 7 8 9 10 ...
\$ V3: int  1 2 3 4 5 6 7 8 9 10 ...
\$ V4: int  3 2 4 3 3 1 3 1 3 2 ...
\$ V5: int  27 16 16 27 27 27 27 27 27 16 ...
\$ V6: int  0 16 16 16 27 27 27 27 16 16 ...
\$ V7: int  6 1 1 2 1 1 1 1 2 1 ...
\$ V8: Factor w/ 151 levels "1.200.995","247.102",..: 1 139 135 39 133
73 142 63 77 67 ...

It's V8 the column we want. The real values are 1 139 135 39 etc. The
levels are categories labels, the categories themselves are the 1-based
integer values.

Anyway, what's important is that the code is working, and if there's an
error maybe it can be solved with this modification:

fun <- function(x, skip = 14){

And the rest is the same. Inspect the file and see if the data starts at
line 15.

(And please, Rui is enough, NO 'Mr.')

Hope this helps,

Em 09-07-2012 14:54, vimmster escreveu:
>
> your solution comes very close to what I want.
>
> But I have two questions left:
>
>
> First question: If "R" computes the mean for the reaction times of test
> subject 34 (the example I provided above), it says "310112.0", but if I use
> the "mean"-function in Excel it says "345.210". Apart from the dots in themaybe
> column of interest (which you mentioned before), the mean is obviously not
> the same. Do you have any idea why?
>
> Second question: Why are the dots in the column of interest problematic?
>
> Kind regards
>
> --
> View this message in context: http://r.789695.n4.nabble.com/Extracting-arithmetic-mean-for-specific-values-from-multiple-txt-files-tp4635809p4635854.html
> Sent from the R help mailing list archive at Nabble.com.
>
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