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

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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 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.

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

Adam Street on 14 Mar 2020
thanks for that, but the massflowrate doesn't change yet...
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)
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
Adam Street on 14 Mar 2020
Subhamoy Saha,
Thank you very much!!!