[R] remove rows of a matrix by part of its row name

[Rui Barradas]

Hello,

Please always cc the list.

As for the question, yes, it does. If you want to remove just the ones 
with exactly 73.1 use the pattern

grep("^73\\.1$", etc)

Explanation:

Beginning of string: ^
End of string: $
Escape special characters: \\ (needed because the period is a special 
character.)

Hope this helps,

Rui Barradas

On 5/22/2018 12:50 PM, Ahmed Serag wrote:
> Thank you Mr. Barradas. The code works great. Unfortunately I have also 
> some labeles with
> 
> 
> 173.1
> 
> 273.1
> 
> 
> the grep script remove them also ?
> 
> Any ideas Plz, Thanks again
> 
> 
> ************************
> 
> *Ahmed Serag*
> 
> /Analytical Chemistry Department/
> 
> /Faculty of Pharmacy/
> 
> /Al-Azhar University/
> 
> /Cairo/
> 
> /Egypt/
> 
> 
> 
> ------------------------------------------------------------------------
> *From:* Rui Barradas <ruipbarradas using sapo.pt>
> *Sent:* Tuesday, May 22, 2018 1:34 PM
> *To:* Ahmed Serag; r-help using r-project.org
> *Subject:* Re: [R] remove rows of a matrix by part of its row name
> Hello,
> 
> Use grep to get the row indices and then subset with a *negative* index
> to remove those rows.
> 
> rn <- scan(what = character(), text = "
> 70/556
> 71.1/280
> 72.1/556
> 72.1/343
> 73.1/390
> 73.1/556
> ")
> 
> mat <- matrix(rnorm(6*6), nrow = 6)
> row.names(mat) <- rn
> 
> inx <- grep("73\\.", row.names(mat))
> 
> new_mat <- mat[-inx, ]
> new_mat
> 
> 
> Hope this helps,
> 
> Rui Barradas
> 
> On 5/22/2018 11:48 AM, Ahmed Serag wrote:
>> Dear R-experts,
>> 
>> 
>> How can I remove a certain feature or observation by a part of its name. To be clear, I have a matrix with 766 observations as a rows. The row names are like this
>> 
>> 70/556
>> 71.1/280
>> 72.1/556
>> 72.1/343
>> 73.1/390
>> 73.1/556
>> Now I would like to remove all the rows that contain the text 73.1
>> 
>> Any ideas or suggestion please ?
>> 
>> 
>> Regards
>> 
>> 
>> 
>> 
>> **********************
>> 
>> Ahmed Serag
>> 
>> Analytical Chemistry Department
>> 
>> Faculty of Pharmacy
>> 
>> Al-Azhar University
>> 
>> Cairo
>> 
>> Egypt
>> 
>>        [[alternative HTML version deleted]]
>> 
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