#Y is the vector of dependent variable
#xpbest is the matrix of independent variables
#of the best model


nsim=100

rmseskill=1:nsim
corskill=1:nsim
index=1:legnth(Y)

for(i in 1:nsim){

d10 = sample(1:length(Y),10,replace=FALSE)
indexkeep=setdiff(index,d10)
Ykeep=Y[indexkeep]
Xpkeep = Xpbest[indexkeep,]

tempmod = lm(Ykeep ~ ., data=Xpkeep)

yhat = predict(tempmod,newdata=Xpbest[d10,])
rmseskill[i]=mean(((Y[d10]-yhat)/sd(Y[d10]))^2)

corskill[i]=cor(Y[d10],yhat)
}

### boxplot corskill and rmseskill
### and overlay coryhat and rmseyhat
## i.e. the values from the model fit without
### dropping