Hello Berend.

Many thanks for your prompt reply and that helped me a lot. One more 
thing, if you please explain, I shall be highly obliged.
Why in my case (i.e. when stringsAsFactors was TRUE by default), 
> as.numeric(matr1$Pulse_rate) 
displays the following
 [1]  4  5  7  5  9  8  6 10  3  2  5  1 10 10
?

Best regards.


From:
Berend Hasselman <bhh@xs4all.nl>
To:
Aniruddha Mukherjee <aniruddha.mukherjee@tcs.com>
Cc:
R-help <r-help@r-project.org>
Date:
02/29/2012 03:57 PM
Subject:
Re: [R] Error occurred during mean calculation of a column of a data 
frame, which is apparently contents numeric data




On 29-02-2012, at 09:45, Aniruddha Mukherjee wrote:

> Hello R people,
> 
> How can I compute the mean of the "Pulse_rate" column of the data frame 
or 
> matrix from the following character object called "str_got". It has 14 
> entries and each entry has 8 values, separated by commas. Please go thru 

> the following R commands to know how I tried to unstring and unlist the 
> values to form a data frame.
>> str_got
> [1] 
"bp,67,2011-12-09T19:59:44.044+05:30,9830576102,68.0,124.0,58.0,66.0" 
> "bp,67,2011-12-09T20:19:31.031+05:30,9830576102,72.0,133.0,93.0,40.0" 
> .....
>> 
> matr<-matrix(unlist(strsplit(str_got, ",")), nrows, byrow=T)

nrows? 
I assume this was set somewhere in your script and not shown.
Is it length(str_got)?

>> matr
>        [,1]   [,2]                                              [,3]  
>       [,4]               [,5]        [,6]       [,7]       [,8] 
> [1,] "bp" "67"    "2011-12-09T19:59:44.044+05:30" "9830576102" "68.0" 
> ......

> Note column names must be inserted before computing the desired mean 
> value.
> matr1<-as.data.frame(matr)

Use matr1 <- as.data.frame(matr, stringsAsFactors=FALSE)

If you don't dos tringsAsFactors=FALSE the column will be a factor and 
that is not equivalent with numeric.

What's wrong with

matr1$Pulse_rate <- as.numeric(matr1$Pulse_rate)

Then you can calculate the desired mean with 

mean(matr1$Pulse_rate)

or

mean(matr1[,"Pulse_rate"])

Berend



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