MATLAB: For Loops and Plotting

for loopsplotting

The following is a for loop. Just checking to make sure it is set up right. Also, when I go to plot this array and an array from 0 to 250 by 0.5, it doesn't work. In my code, it is "plot(timearray,resultarray)" and doesn't work. Any suggestions?

Thanks

for i = (0:.5:250) 
    resultarray = (((array(6,:) * array(2,:)) / (constant - array(6,:))) * (exp(-array(6,:) * i * 3600) - exp(-constant * i * 3600))) + (array(1,:) * exp(-constant * i * 3600));
end

Best Answer

You need to subscript ‘resultarray’, and also ‘timearray’, to create a vector out of each one:

for k1 = (0:.5:250) 
    resultarray(k1) = (((array(6,:) * array(2,:)) / (constant - array(6,:))) * (exp(-array(6,:) * i * 3600) - exp(-constant * i * 3600))) + (array(1,:) * exp(-constant * i * 3600));
end

I changed your loop index counter to ‘k1’ because MATLAB uses i and j as its imaginary operators.

That is particularly significant here, because if ‘i’ is an index will produce the exponent of a real argument, exp(-constant*i*3600), but if it you intend it to be the imaginary operator, will return cos(constant-3600)-i*sin(constant*3600).

I left it as ‘i’ in your calculation for ‘resultarray’ because I have no idea what you intend. Neither does MATLAB.

Related Solutions

MATLAB: Help Calling a Function

You can't start out myHW7.m with these lines:

function constant = reaeration(array)
function resultarray = deOxygen(array , constant)

Those are function definitions which you define later in the m-file. So you're basically doing it twice and the first time you define them there's not even any body to the function. So, I assume you just want to call them, but to call them you need a function line with myHW7 in it:

function myHW7()
    load PollutionData.txt;
    array = PollutionData(:,1);
    timearray = (0:.5:250);
    % Now call (not define) the functions
    constant = reaeration(array)
    resultarray = deOxygen(array , constant)
      return
% Now define other functions like reaeration() and deOxygen()

MATLAB: Help solving an error

In ‘deOxygen’, define the ‘a’ vector first:

a = (0:.5:250);

then set the loop up as:

for k1 = 1:length(a)

and replace the ‘(a)’ subscripts with ‘(k1)’ subscripts (or whatever loop counter variable you choose). MATLAB does not allow subscripts to be negative, zero, or non-integers.

Also, I’m not sure what ‘a’ is doing. You don’t use it anywhere in ‘deOxygen’ that I can find.

Best Answer

Related Solutions

MATLAB: Help Calling a Function

MATLAB: Help solving an error

Related Question