Populate an array with given values

[Jody Monahan]

Hi,


I have a really basic question here and it has been driving me up the wall all day .....how do I populate an array with values between 500 and 3000 with increments of 0.05?
I have tried the following:

float minf = (float)500;
float maxf = (float)3000;
float delta = (float)0.05;

float length = (maxf-minf)/delta;

// array to be populated
float[] Fc = new float [length];

for(float i=500; i< 3000; i += 0.05 ) 
{ 
    Fc[i] = i;
	System.out.println("i is " + Fc[i]);
}

The current error I get with the above code is that I cannot convert from float to int for the iterator 'i'. I have tried umpteen different variants of the above code but to no avail.
i am sure I am making a small error here and I appreciate any help given.

Thanks.

[Rob Spoor]

Your index starts at 0 and increments with 1. If you could have declarations of different types in a for loop you would want the following:

for (int i = 0, float f = 500; i < Fc.length; i++, f += 0.05) // compiler error though
{    
    Fc[i] = f;   
    System.out.println("i is " + Fc[i]);   
} 

You will need to move the declaration of either i or f outside the for-loop. Alternatively, you could drop f completely and recalculate its value each time:

Fc[i] = 500 + i * 0.05F;

[fred rosenberger]

note that you will quickly get rounding errors...

[Jody Monahan]

note that you will quickly get rounding errors...

Is there anyway to eliminate this round off error?

When I compiled the code, my maximum value went up to 3256.2 rather than 3000....I presume the round-off error is to blame for this?

Cheers.

[Jody Monahan]

Sorry, I was mistakingly using different values there and I do get a value of in and around 3000 (2999.95) to be exact. But my question still stands about eliminating the roundoff error, is it possible?

Thanks again!

[fred rosenberger]

you may want to read item #20 in our JavaBeginnersFaq, and then follow the links there.

[Jody Monahan]

Will do, thanks!

[Charles Bradley]

First, figure out how big the array should be. You were close with (end-start)/step. The answer should be an integer. Hint: suppose the end was 501 instead of 3000. Second, make a short list on a piece of paper, the index and the value to place at the index, like this:
0 500.00
1 500.05
2 500.10
3 500.15
Then figure out the formula for the value when the index is given.
Then write the code, a for loop with the integer index and the end point you calculated, and a body of one assignment with the formula you figured out.
(edited to change 50 to 500.)