# [R] (no subject)

Peter Ehlers ehlers at ucalgary.ca
Tue May 18 18:24:55 CEST 2010

```Arantzazu,

Your problem is that the data were probably imported
from Excel where you had at least one cell containing "#N/A".
You need to replace those cases in your dataframe with NA.
Then you should be able to do as.numeric(as.character(arcilla)).

-Peter Ehlers

On 2010-05-18 10:07, Arantzazu Blanco Bernardeau wrote:
>
> Hello
> Well, the problem is, that arcilla is the percentage of clay in the soil sample. So, for linear model, I need to work with that number or value. Now, R thinks that arcilla (arcilla means clay in spanish), is a factor, and gives me the value as a factor, so the output of the linear model is
> Call:
> lm(formula = formula, data = caperf)
>
> Residuals:
>         Min         1Q     Median         3Q        Max
> -1.466e+01 -1.376e-15  1.780e-16  2.038e-15  1.279e+01
>
> Coefficients:
>                Estimate Std. Error t value Pr(>|t|)
> (Intercept)    1.68964    6.33889   0.267 0.790221
> arcilla0.9     1.90228    8.90888   0.214 0.831239
> arcilla10      1.26371    7.96734   0.159 0.874212
> arcilla10.3   15.70081    9.05141   1.735 0.085090 .
> arcilla10.4    7.27517    7.72806   0.941 0.348183
> arcilla10.45   7.03879    9.02600   0.780 0.436853
> arcilla10.5    2.41241    8.90827   0.271 0.786954
> arcilla10.65  15.44298    9.03879   1.709 0.089838 .
> arcilla10.7   19.35651    9.04675   2.140 0.034185 *
> arcilla10.9    3.55947    9.18501   0.388 0.698974
>
> [...]
>
> arcilla9.9     6.31949    7.35724   0.859 0.391892

===> arcilla#N/A   24.17959    8.87201   2.725 0.007274 **

> limo           0.24920    0.04605   5.412 2.76e-07 ***
> CO_gkg1        0.21015    0.03931   5.346 3.73e-07 ***
> C03Ca          0.01711    0.02727   0.628 0.531337
> ---
> Signif. codes:  0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1
>
> Residual standard error: 6.249 on 135 degrees of freedom
>    (50 observations deleted due to missingness)
> Multiple R-squared: 0.9736,    Adjusted R-squared: 0.9014
> F-statistic: 13.47 on 370 and 135 DF,  p-value:<  2.2e-16
>
> So, in the desired linear model, arcilla should be just a line, with the valors of the linear model.
> I hope you understand better more. If not, I could make an english version of the file to send, so you can try the commands.
> Thanks a lot for your help!
>
>
>
> Arantzazu Blanco Bernardeau
> Dpto de Química Agrícola, Geología y Edafología
> Universidad de Murcia-Campus de Espinardo
>
>
[snip]

```