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]
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