[R] question on mean, sum

[Berend Hasselman]

In addition to Petr's remarks:

- why are you doing sum(mtcars)[1]?  Do you want the sum of first column of mtcars? In that case you should do sum(mtcars[,1]).

- similar remarks apply to your use of  mean and sd.


Have you read an introduction to R?


Berend

> On 14 Nov 2016, at 04:01, mokuram at sina.com wrote:
> 
> Hi, 
> I am working on functions such as sum(), mean() ... 
>> sum(mtcars)[1] 13942.2> mean(mtcars)[1] NAWarning message:In mean.default(mtcars) : NA> sd(mtcars)Error in is.data.frame(x) : ()'double'
> why got different reply?Is this a BUG for the current version of R?my version info:version.string R version 3.3.1 (2016-06-21)
> 
> Thank you very much for the help.
> mokuram
> 
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