I used the following script to calculate AUC in R:

library(mgcv)
library(ROCR)
library(AUC)

data1=read.table("d:\\2005.txt", header=T)
GAM<-gam(tuna ~ s(chla)+s(sst)+s(ssha),family=binomial, data=data1)

gampred<- predict(GAM, type="response")

rp <- prediction(gampred, data1$tuna) 

auc <- performance( rp, "auc")@y.values[[1]]
auc

roc <- performance( rp, "tpr", "fpr")
plot( roc )

But when I was running the script, the result is:

 **rp <- prediction(gampred, data1$tuna) 
Error in prediction(gampred, data1$tuna) : 
  Format of predictions is invalid.
> 
> auc <- performance( rp, "auc")@y.values[[1]]
Error in performance(rp, "auc") : object 'rp' not found
> auc
function (x, min = 0, max = 1) 
{
    if (any(class(x) == "roc")) {
        if (min != 0 || max != 1) {
            x$fpr <- x$fpr[x$cutoffs >= min & x$cutoffs <= max]
            x$tpr <- x$tpr[x$cutoffs >= min & x$cutoffs <= max]
        }
        ans <- 0
        for (i in 2:length(x$fpr)) {
            ans <- ans + 0.5 * abs(x$fpr[i] - x$fpr[i - 1]) * 
                (x$tpr[i] + x$tpr[i - 1])
        }
    }
    else if (any(class(x) %in% c("accuracy", "sensitivity", "specificity"))) {
        if (min != 0 || max != 1) {
            x$cutoffs <- x$cutoffs[x$cutoffs >= min & x$cutoffs <= 
                max]
            x$measure <- x$measure[x$cutoffs >= min & x$cutoffs <= 
                max]
        }
        ans <- 0
        for (i in 2:(length(x$cutoffs))) {
            ans <- ans + 0.5 * abs(x$cutoffs[i - 1] - x$cutoffs[i]) * 
                (x$measure[i] + x$measure[i - 1])
        }
    }
    return(as.numeric(ans))
}
<bytecode: 0x03012f10>
<environment: namespace:AUC>
> 
> roc <- performance( rp, "tpr", "fpr")
Error in performance(rp, "tpr", "fpr") : object 'rp' not found
> plot( roc )
Error in levels(labels) : argument "labels" is missing, with no default**

Can anybody help me to solve this problem? Thank you in advance.