R help - Feb 2010 - Deleting colmuns with 0's and also writing multple csv files

Dear R helpers,
 
I have two queries.
 
(1) If the dataset contains some variables having all the entries = 0 and while
analysing I want to delete those pericular columns, how do acheive this. i.e.
 
dataset1
 
sr_no    var1      var2       var3        var4        var5
1           5           0          3              1           0
2           3           0          2              9           0
3           4           0          4              7           0 
4          11          0          1              6           0
 
In the above dataset, var2 and var3 are all 0's so I don't want to
select these columns. It is not that always these two variables will be zeros,
so in general how the dataset can be filtered in order to have only non-zero
columns.
 
(2)  Suppose I have variable no of datasets 'say n = 10'. I wish to
write a loop assigning each of these datasets to diffrent csv files e.g.
 
for (i in 1:10)
 {
write.csv(data.frame(dataset[,,i]), 'data_set[i].csv', row.names =
FALSE)
 }

The result of this command is generation of a csv file 'data_set[i].csv'
containing the last dataset (owing to the wrong command written by me).
 
What I need is creation of say data_set[1].csv, data_set[2].csv, 
.........data_set[10].csv i.e. 10 different csv files containing 10 different
datasets.
Thanking you in advance

Anna
 


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Dear Anna,

19.02.2010 08:17, Anna Carter wrote:
> (1) If the dataset contains some variables having all the entries = 0
> and while analysing I want to delete those pericular columns, how do
> acheive this. i.e.
Let's suppose 'df' is your data frame, then:

subset(df, select=which(colSums(df)!=0))

should do the work :)

HTH,
Kimmo

Hi Anna,

A column with all 0s will have a column sum of zero. So do this :

dataset1[, which(colSums(dataSet1 > 0))]

If you have a list of data.frames you could do this

for(index in 1:10)
{
        write.csv(yourListOfTables[[index]], file = paste("Dataset",
index,
".csv", sep = ""), row.names = FALSE)
}

- Dario.
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> (2)? Suppose I have variable no of datasets 'say n = 10'. I wish to
write a loop assigning each of these datasets to diffrent csv files e.g.
>
> for (i in 1:10)
> ?{
> write.csv(data.frame(dataset[,,i]), 'data_set[i].csv', row.names =
FALSE)
> ?}
>
> The result of this command is generation of a csv file
'data_set[i].csv' containing the last dataset (owing to the wrong
command written by me).
>
> What I need is creation of say data_set[1].csv, data_set[2].csv,?
.........data_set[10].csv i.e. 10 different csv files containing 10 different
datasets.

Why do you want to create csv datasets?  They lose much of the
structure that is in the R object.
If you are trying to transfer them to somewhere else, then a direct
transfer would be a better choice.

If the goal is Excel, there are about 5 options.  I prefer RExcel
because it allows the tightest
coordination of the R and the Excel calculations.

If the goal is one of the other popular statistical systems, they also
have direct connections,
often through the foreign package.

Rich