MATLAB: Plotting Error (Very Simple Code)

plotting error

As part of practice of plotting, I made a very simple code, but it has an error. Would you check the code and explain on the problem so that I can make an correction?

x=1.0:0.2:2.0; y=2/x; plot(x,y)

Error using / Matrix dimensions must agree.

Error in Untitled6 (line 2) y=2/x;

Best Answer

y = 2./x;

The operation A/B is like A * inv(B) where * is algebraic matrix multiplication. You want element-by-element division, which is the ./ operator

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MATLAB: Simple problem about plotting

When you multiply a vector by another vector element by element, you need to use .* instead of * otherwise it tries to do a matrix multiplication. Fixed code:

y=(x+895.185).*(42.036*sqrt(x+657.509)-1656.4)-42.036*sqrt(x+657.509).*(x+1790.37)+2234.91*x+2.484*10.^6;

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The "x trick" you are using is actually the element-wise exponentiation. MATLAB is inherently a matrix language (MATrix LABoratory) and by default it wants to do matrix computations.

So, the reason for your error is that you need to be using element-wise division too. Again, use the . to make it element-wise.

>> y = 6 - 400./(100+x.^2)

The reason it worked when x was in the numerator is because dividing or multiplying by a scalar is a special case that MATLAB makes an exception for.

Best Answer

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