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I would like to change the massflowrate when the statement is correct, could you help?

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Adam Street
Adam Street on 14 Mar 2020
Commented: Adam Street on 14 Mar 2020
For some reason the massflowrate doesn't change itself whenever I enter the following, no errors or anything appear. Just got no clue how to fix this.
electricalsignal=5;
massflowrate=3;
if electricalsignal==0
disp("error")
else
temperature = 200*electricalsignal-400;
end
if temperature<74;
disp("opening valves")&& massflowrate == massflowrate-50;
elseif (74<=temperature) && (temperature>=78)
disp("closing valves")
elseif temperature>78
disp("closing valves") && massflowrate == massflowrate+50;
endif

  1 Comment

Guillaume
Guillaume on 14 Mar 2020
I would strongly recommend that you go through the free matlab onramp to learn the basics of matlab.
I'm not entirely sure what you're trying to achieve with these lines:
disp("opening valves")&& massflowrate == massflowrate-50;
it's a completely made up syntax.

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Accepted Answer

Subhamoy Saha
Subhamoy Saha on 14 Mar 2020
Edited: Subhamoy Saha on 14 Mar 2020
The problem is with the line you are changing values of massflowrate. You are making it logical condition rather assigning it a new value. Please try the following
electricalsignal=5;
massflowrate=3;
if electricalsignal==0
disp("error")
else
temperature = 200*electricalsignal-400;
end
if temperature<74;
disp("opening valves"), massflowrate = massflowrate-50; % corrected
elseif (74<=temperature) && (temperature>=78)
disp("closing valves")
elseif temperature>78
disp("closing valves"), massflowrate = massflowrate+50; % corrected
end

  5 Comments

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Subhamoy Saha
Subhamoy Saha on 14 Mar 2020
Dear Adam, the massflowrate is not changing beacause for electricalsignal=5 temperature=600 which satisfies your second elseif condition and doesnot change massflowrate (as there is not conditions in your code). Actually there is a problem in your second elseif condition. I think you want to imply
elseif (74<=temperature) && (temperature<=78)
Please correct this condition as per your need.
However, the solution I provided is working fine. Just change the electricalsignal value to something else like 2.1 or so. For its value 3 it is going to your second elseif condition.
Anyway, here is the full corrected code
electricalsignal=5;
massflowrate=3;
if electricalsignal==0
disp("error")
else
temperature = 200*electricalsignal-400;
end
if temperature<74;
disp("opening valves"), massflowrate = massflowrate-50; % corrected
elseif (74<=temperature) && (temperature<=78) %% corrected
disp("closing valves")
elseif temperature>78
disp("closing valves"), massflowrate = massflowrate+50; % corrected
end % corrected

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