Making Array Change Based on KeyCode

I'm trying to use the code below to make the arrayGroup contain the data set relevant to keystrokes up or down. Depending on this it will add or subtract one from the variable named numberArray1 and allow different arrays to be called depending on which data set arrayGroup is being set to. Currently I can call the arrays as strings, but I am having trouble calling them as arrays and passing them into arrayGroup.

Your advice would be greatly appreciated!!!

var arrayGroup = [];

var numberArray1 = [1,2,3,4,5,6,7,8,9,10];

var numberArray2 = [10,11,12,13,14,15,16,17,18,19];

x=0;
alert(x);
document.addEventListener('keydown', function (evt) {
    if (evt.keyCode === 38) {
        alert('The "UP" key is being held down...?');
        alert(numberArray1);
        x=x+1;
        alert(x); 
        alert ("numberArray"+(x));
        arrayGroup = "numberArray"+(x);
        alert(arrayGroup);


    }
    if (evt.keyCode === 40) {
        alert('The "DOWN" key is being held down...?');
        arrayGroup = "numberArray"+(x-1);
        x=x-1;
        if(x<0){
            x=0;
            arrayGroup = "numberArray0";
        }

        alert(x);
        alert(arrayGroup);
    }
});

Update!!! - I am still having trouble with this...

Hello,

The purpose of the code below is to update an SVG map with RGB values relative to the data taken from the numberArrays. Every time the user uses the cursor I want to cycle through different arrays, which in turn will allow the map to change colour. Currently I am having difficulty with the global variable arrayGroup, I am unable to make the rest of the code interpret the updated arrays on keypress.

Any advice that can be offered would be greatly appreciated.

Many thanks!!!

var rsr = Raphael('map', '595.28', '841.89');

counties = [];

//obviously, this is the array storing the numbers of students for this particular year
numberArray0 =     [46,54,38,125]:    
//this empty array will store the different number categories i.e. 0-50, 51-100...
categories = [];

var arrayGroup = [];

numberArray1 = [460,200,384,135]:  

numberArray2 = [260,100,584,335]:

x=0;

if(x===0){
    arrayGroup = numberArray0;
    alert(arrayGroup);}

document.addEventListener('keydown', function (evt) {
if (evt.keyCode === 38) {
    alert('The "UP" key is being held down...?');
    x+=1;
    arrayGroup = eval ("numberArray"+(x));
    alert(arrayGroup);


}
if (evt.keyCode === 40) {
    alert('The "DOWN" key is being held down...?');
    arrayGroup = eval ("numberArray"+(x-1));
    x-=1;
    alert(arrayGroup);
        if(arrayGroup===numberArray+(-1)){
        x=0;
        alert(numberArray0);}
}
});

//this for loop populates the "categories" array with these categories, going up in       fifties (i=0; i<61 becuase 60*50=3000, the number we were taking as the highest
for(i=0; i<61; i++){
if(i==0){
categories[0]=0;   
}
else{
categories.push(categories[i-1]+50);
}
};

//empty array that will store the strings that define the colour of the counties
colourStrings=[];

//this loop goes through the population numbers for the county and finds out what category    they are.
for(var i=0; i<arrayGroup.length; i++){
for(var j=0; j<categories.length; j++){
// this is a loop within a loop. First it takes a population number and runs through all     the categories to see which one it's in
if(arrayGroup[i]>categories[j]){
//if it's bigger than the start point of the category(e.g. 71 is bigger than 50, goes in      the 51-100 bracket) we take the index 
index=j;
}


}
//the higher the category the population is in, the higher the index will be and the more     the g and b values will be reduced
//the colour value wll then be stored in colourStrings at an index that corresponds with     the county
colourStrings.push("rgb(255,"+(250-4*index).toString()+","+ (250-4*index).toString()     +")");
}