Taking input for arrays - c

Question

In doing a project for my computer science class, I came upon a problem with arrays. Basically, I have to take an input from the user for the number of years they want to input data for. I then have to use that input to create two arrays (one for the actual years they want the data for, and one for the data itself). I then have to print out the years and the data that the user just input.
The problem is that when I do this, the data for the years prints out fine, but the years themselves print out as random memory addresses. The other strang thing is that this only happens when I do three or more years. When I do two or less, everything else is fine. The variable for the years is an int and the variable for the data is a double.
int numberofyears;
printf("Enter the number of years you wish to take data for: " );
scanf("%d",&numberofyears); //take input for how many times arrays run
int years[numberofyears];
double dataforyear[numberofyears];
int a;
printf("Enter the years and their respective data");
for (a=0;a<numberofyears;a++){
scanf("%d %lf",&years[a],&dataforyear[a]);} //take inputs for both arrays
int b;
for (b=0;b<numberofyears;b++){
printf("%d %.2lf\n",years[b],dataforyear[b]);}
Input of:
Enter the number of of years you wish to take data for: 5
Enter the years and their respective data
1950 200.96
2000 300.55
Prints out:
1950 200.96
2000 300.55
Input of:
Enter the number of of years you wish to take data for: 5
Enter the years and their respective data
1956 325.21
1989 386.22
2003 400.00
Prints out:
0 325.21
1081671680 386.22
2003 400.00
And anything else beyond 3 years will do this. Though it seems like things beyond 5 years do not keep the last year like 3 does for whatever reason, if that helps.

Answer 1

How have you declared your dataforyear[] array?
If it is float dataforyear[] then change your scanf statement to
scanf("%d %f",&years[a],&dataforyear[a]);
else declare your array to double dataforyear[] if you want to keep yourscanf statement as it is.

Answer 2

These lines:
int years[numberofyears];
double dataforyear[numberofyears];
might be the problem. The compiler needs to know the size of your arrays at compile time. Otherwise you will have to allocate memory for your arrays. If your program isn't expected to read in a lot of data, you could always avoid allocating memory by specifying their sizes.
int years[10];
double dataforyear[10];