Write results from stepAIC to a table - r

Question

I am trying to write r2, rmse, coefficients, and standardized coefficients from stepAIC to a .CSV file:
NO3_lmres_ClimateOnly <- data.frame()
for (i in unique(Data$SeasAlltxt)){
print (i)
subdata1 <- subset(Data, SeasAlltxt == i)
for (j in unique(Data$ALSCIDtxtall)){
subdata2 <- subset(subdata1, ALSCIDtxtall == j)
fit <- lm(NO3resid~Avg94NO3+MaxDepth_m+MaxDepthDOY+FirstZeroDOY+PeakToGone+PRISMppt+PRISMtmax, data = subdata2, na.action = na.omit)
step <- stepAIC(fit, direction="both")
rmse <- round(sqrt(mean(resid(step)^2)), 3)
r2 <- round(summary(step)$r.squared, 3)
coefs <- summary(step)$coefficients
stdcoefs <- lm.beta(step)
stdcoefs <- unname(stdcoefs)
params <- names(stdcoefs)
tempvalues <- data.frame(i,j,rmse,r2,coefs,stdcoefs,params)
colnames(tempvalues) <- c('SeasAlltxt', 'ALSCIDtxtall', 'rmse', 'r2', 'coef', 'stdcoef','param')
NO3_lmres_ClimateOnly <- rbind(NO3_lmres_ClimateOnly,tempvalues)
}
}
write.csv(NO3_lmres_ClimateOnly, file = "NO3_ClimateOnly_stats.csv")
However, the above code produces this error:
Error in data.frame(i, j, rmse, r2, coefs, stdcoefs, params) :
arguments imply differing number of rows: 1, 3, 2, 0
I would also like to write the p-value associated with each parameter to the output table.
Any suggestions for how to accomplish this?

Answer 1

Maybe you want to change your code:
for (j in unique(subdata1$ALSCIDtxtall))
...
coefs <- summary(step)$coefficients[,1]
...
tempvalues <- data.frame(t(c(i,j,rmse,r2,coefs,stdcoefs,params)),stringsAsFactors=F)
colnames(tempvalues ) <- c('SeasAlltxt', 'ALSCIDtxtall', 'rmse', 'r2', names(coefs), paste('stdcoef:',params),params)
Bud the final rbind will give you an error when stepAIC select different number of coefficients.
Think of using a list instead:
Define cont=1 outside the for
then, change the following lines:
tempvalues <- data.frame(t(c(i,j,rmse,r2,coefs,stdcoefs,params)),stringsAsFactors=F)
colnames(tempvalues ) <- c('SeasAlltxt', 'ALSCIDtxtall', 'rmse', 'r2', names(coefs), paste('stdcoef:',params),params)
NO3_lmres_ClimateOnly[[cont]] <- tempvalues
cont=cont+1
Good luck!!