Indentify spcific point of matrixs

currently I have two matrix which is drag and thrust as you see below, and the number of two martix is going to be very close at some point, and I need to find out what the spcific number of drag and thrust when they are really close to each other, I have try to write the flowing function, but it only return the orginal matrix of thrust

function [maxSpeed,thrustDragVal] = maxSpeedThrustCalc(V, thrust, drag)

for difference = thrust - drag

if abs(difference) <= 0.01

maxSpeed = V;

thrustDragVal = thrust;

end

end

Answer 1

[Sriram Tadavarty]

Hi Felix,

I see that the for loop condition is not correct. You can try the following

function [maxSpeed,thrustDragVal] = maxSpeedThrustCalc(V, thrust, drag)
for i = 1:length(thrust)
    difference = thrust(i) - drag(i);
    if abs(difference) <= 0.01 
        maxSpeed = V;
        thrustDragVal = thrust(i);
    end
end
end

% You mentioned that drag and thrust need to be known, but i am not sure why the output is set to maxSpeed
% You indicate the minimum difference, but why is the threshold placed as 0.01
% If both the above is same as what is said, you need to use the following code
difference = thrust - drag;
[m,i] = min(abs(difference)); % m is the minimum value and i is the index where minimum occurs
thrustVal = thrust(i);
dragVal = drag(i);

Hope this helps.

Regards,

Sriram

[Felix Hao]

Sorry I forgot to mention that drag is calculated by a number mutiply by 1*2401 vector called V, and thrust is also calculated by some number mutiply by V vector. So V is like the x axis of drag and thrust, so I need to return the value of their intersection point(not actually intersected just close to each other) and the V value at that point which is the maxSpeed I need to know.

Thank You!

[Sriram Tadavarty]

ok.. So if you index V(i) that should give you what is required.

[Felix Hao]

Thank you sir!

[Felix Hao]

Sorry Sir, I hate to bother you again, but do you know how can I make it only return the intersection on the right, now it return the intersection point on the left.

Really Appreciate it !

The functioin I used:

function [maxSpeed,thrustDragVal] = maxSpeedThrustCalc(V, thrust, drag)

for difference = drag - thrust

[m,i] = min(abs(difference));

if (abs(difference) == m)

maxSpeed = V(i);

thrustDragVal = thrust(i);

end

end

end