[R] GLM HELP NEEDED!

[Duncan Murdoch]

On 01/02/2017 8:28 AM, CHIRIBOGA Xavier wrote:
> Dear colleagues,
>
>
> I am trying to perform a GLM. I tried again without using attach()...but still is not working.
>
> Do you have any idea to help me?
>
>
> Thank you again,
>
>
> Xavier
>
>
>
> a <- read.table(file.choose(), h<-T)

The "h<-T" argument doesn't make sense.  You are just lucky that it 
worked here. For arguments you almost always use "=".

It's also a bad idea to use "T" as an abbreviation for "TRUE", but that 
won't always cause problems.

>> head(a)
>   time treatment transinduc
> 1    1   CHA0+Db     1,0768
> 2    1   CHA0+Db     1,0706
> 3    1   CHA0+Db     1,0752
> 4    1   CHA0+Db     1,0689
> 5    1   CHA0+Db     1,1829
> 6    1    PCL+Db     1,1423

I assume that transinduc is supposed to be real numbers, with comma as 
the decimal separator.  You need to use dec = "," in read.table to read 
that properly.

>> summary(a)
>       time         treatment    transinduc
>  Min.   :1.000   CHA0   :10   1,0488 : 6
>  1st Qu.:1.000   CHA0+Db: 9   1,0724 : 4
>  Median :1.000   Db     : 9   1,0752 : 3
>  Mean   :1.433   HEALTHY:15   1,0954 : 3
>  3rd Qu.:2.000   PCL    :10   1,0001 : 2
>  Max.   :2.000   PCL+Db :14   1,0005 : 2
>                               (Other):47
>> m1<-glm(a$transinduc~a$time*a$treatment,data=a,family="poisson")
> Error in if (any(y < 0)) stop("negative values not allowed for the 'Poisson' family") :
>   valor ausente donde TRUE/FALSE es necesario
> Adem�s: Warning message:
> In Ops.factor(y, 0) : '<' not meaningful for factors

It doesn't make sense to use fractional values like 1.0488 in Poisson 
regression.

Duncan Murdoch