Program does 5 calculations instead of one.
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Hi Guys! I have written a simple script, that's supposed to do some loop calculations. Here's the script:
a=3;
initialVelocity = 38.8889;
brakeMass = 14;
velocity = (initialVelocity:a:54.72);
coolingCoef = (85+0.0017*velocity.^2);
A=0.4;
time=(velocity-initialVelocity)/a;
temperature = zeros(1,6);
temperature(1)=900;
for x=2:length(temperature)
dissipatedHeat = coolingCoef.*(temperature(x-1))
energy = dissipatedHeat.*time;
specificHeatCapacity = 457+0.14219*temperature(x-1);
temperatureDrop = energy/(brakeMass*specificHeatCapacity);
temperature(x)=temperature(x-1)-temperatureDrop(x);
end
When I run the proram it gives me series of answers. Like this:
dissipatedHeat =
1.0e+04 *
7.8814 7.9185 7.9583 8.0009 8.0462 8.0943
dissipatedHeat =
1.0e+04 *
7.7967 7.8334 7.8728 7.9149 7.9598 8.0074
dissipatedHeat =
1.0e+04 *
7.6280 7.6638 7.7024 7.7436 7.7875 7.8340
dissipatedHeat =
1.0e+04 *
7.3778 7.4125 7.4498 7.4896 7.5321 7.5771
dissipatedHeat =
1.0e+04 *
7.0511 7.0842 7.1199 7.1580 7.1985 7.2416
However, I just want the script to multiply value by value. So say on the first iteration it multiplies frst values from the vector and gives me the answer of temperature for second iteration. It the multiplies 2nd value from both matrices and so on. I think Matlab multiplies every member in a matrix by every member in other matrix. I tried adding a do before one of the values, but it does not help. Any ideas how to fix it? Think I'm just missing a small point somewhere,but can't find it. Thank you!
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채택된 답변
Jan
2012년 7월 20일
편집: Jan
2012년 7월 20일
Perhaps you want:
...
dissipatedHeat = coolingCoef(x-1) * (temperature(x-1))
...
energy = dissipatedHeat * time(x); % or time(x-1)?
댓글 수: 3
bym
2012년 7월 21일
I think you should consider Jan's answer more carefully.
coolingCoef
time
are vectors.
Jan
2012년 7월 21일
편집: Jan
2012년 7월 21일
velocity is a vector. Therefore coolingCoef and time are vectors. Therefore dissipatedHeat is a vector. Did you try my suggestion, which let you access one element per loop iteration?
Use the debugger and step through you code line by line to find out, what's going on.
추가 답변 (3개)
Kokalz
2012년 7월 21일
댓글 수: 3
per isakson
2012년 7월 21일
편집: per isakson
2012년 7월 21일
Meta: Comment on comment
It is difficult to read and understand your comment and that is partly because it is not formatted. Now, I have copy&pasted to an editor formatted somewhat and printed.
Compare:
So it goes like this:
- I assign the first value for temperature
- get values for dissipated heat energy and so on, to get the second value of temperature.
- And then it starts all over to get the value of 3rd temperature.
per isakson
2012년 7월 22일
편집: per isakson
2012년 7월 22일
Firstly, the code appears to be a strange blend of loop and vectorized (as Jan says).
Secondly, a short description of the underlying physics would help. Is it about a brake (of a moving vehicle), which heats and losses heat as the velocity of the vehicle changes?
Thirdly, I think it would be helpful to indicate physical units in comments to appropriate assignments.
Time out for now. I'll have a look at your code in my next break.
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