# NaN Issues with Libraries

Link to the project or level:

What I expect to happen:
I am a first year teacher, and am having trouble explaining to my student the error that is resulting in a NaN console log output…

What actually happens:
Instead of calculating the averages, like intended, it is only returning NaN

The NaN problem can be fixed pretty easily, just change `var total` to `var total = 0` on line 7.
But it has a couple other small issues that prevent it from calculating correctly. This revised function should do the trick:

``````function calculateAverage(list) {
var total = 0;
for (var i = 0; i < list.length; i++) {
total+=list[i];
}
var avg = total / list.length;
return avg;
}
``````

The combining function can be improved by having it fuse the two lists together and then averaging them:

``````function combineAverages(arr1, arr2) {
var combinedAvg = calculateAverage(arr1.concat(arr2));
return combinedAvg;
}
``````

And if you’re interested in a different way to average lists, this one will do it without a loop:

``````function average(arr) {
return Math.round((arr.reduce(function(a, b) {return a+b}) / arr.length));
}
``````
1 Like

THANK you! I appreciate your help!! It is always something so blatantly obvious!