This code doesn't print graph as expacted $,$ how can I fix it$?$ See athachedset.seed$(6522048)$

library $($randomForest$)$

# Root mean squared error

RMSE $=$ function$($pred$,$ obs$)\{$

return$($sqrt$($ sum$(($pred $-$ obs$)^2)/$length$($pred$)))$

$\}$

# checking

train $=c()$

test $=c()$

trees $=c()$

for $($i in seq$($from$=1,$ to $=150,$ by$=1))\{$

trees c$($trees$,$ i$)$

model$\_$rf randomForest$($target $$ age $+$ sex $+$ cp $+$ trestbps $+$ chol $+$ restecg $+$ exang $+$ ca$,$ data $=$ heart$\_$data, ntree $=$ i$)$

pred predict$($model$\_$rf$7,$ newdata$=$train.data, type$=$'response'$)$

rmse$\_$train RMSE $($pred$,$ train.data$target$)$

train c$($train$,$ rmse$\_$train$)$

pred predict$($model$\_$rf$7,$ newdata$=$test.data, type$=$'response'$)$

rmse$\_$test RMSE $($pred$,$ test.data$target$)$

test c$($test$,$ rmse$\_$test$)$

$\}$

plot$($trees$,$ train,type $="$l$",$ylim$=$c$(20,130),$ col $=$ "red", xlab $=$ "Number of Trees", ylab $=$ "Root Mean Squared Error"$)$

lines$($test$,$ type $="$l$",$ col $=$ "blue"$)$

legend$(\text{'}$topright$\text{'},$ legend $(\text{'}$training set','testing set'$),$ col $=c(red,$blue$),lwd=2$