R help - Mar 2008 - Combining logical operators to extract columns from a dataframe

Hi R-helpers,

I have a dataframe (called data) with 100 columns, the columns of which are
named with integers ranging from 1900 to 1999.

I wish to extract those columns which names are >=1950 and <=1970.

I tried:

data2<-subset(data,select=(names(data)>=1950 & names(data)<=1970))

but that doesn't work.

Any ideas?

Thanks! Mark

	[[alternative HTML version deleted]]

mtb954 at gmail.com wrote:
> Hi R-helpers,
> 
> I have a dataframe (called data) with 100 columns, the columns of which are
> named with integers ranging from 1900 to 1999.
> 
> I wish to extract those columns which names are >=1950 and <=1970.
> 
> I tried:
> 
> data2<-subset(data,select=(names(data)>=1950 &
names(data)<=1970))
> 
> but that doesn't work.
> 
> Any ideas?
## untested

data[as.character(1950:1970)]

> 
> Thanks! Mark
> 
> 	[[alternative HTML version deleted]]
> 
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.

mtb954 at gmail.com wrote:
> Hi R-helpers,
>
> I have a dataframe (called data) with 100 columns, the columns of which are
> named with integers ranging from 1900 to 1999.
>
> I wish to extract those columns which names are >=1950 and <=1970.
>
> I tried:
>
> data2<-subset(data,select=(names(data)>=1950 &
names(data)<=1970))
>
> but that doesn't work.
>
> Any ideas?
>
>   
The subset() function and in particular its select argument is playing 
tricks with the evaluation rules, mostly to be helpful, but sometimes 
apparently not...

Ordinary indexing should work:

data[, names(data) >= "1950" & names(data) <=
"1970"]

(using quoted strings to emphasize that you are really comparing 
alphabetically. That is probably OK here, but beware that

 > "999" > 1999
[1] TRUE

Also, BTW, check that names really are "1950", not "X1950"
or so. Data
frame methods like to rationalize column names to be valid variable names.)
> Thanks! Mark
>
> 	[[alternative HTML version deleted]]
>
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>   

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