MATLAB: Simple MATLAB (noob) question

graphingMATLABnoob

Hello,

I not a frequent user to this program and I'm running into a little problem regarding graphing a function.

First I input this: x = 0:pi/15:4*pi

so that I can develop a range of the x values next I enter: y = (2*cos(60*x))

but it all comes out equaling two, when it shouldn't. I don't know where I'm going wrong. Help would be appreciated.

Best Answer

The way you set your x vector and then multiply by 60, you have increments of 4*pi (60*(pi/15)). Since you evaulate the cosine of angles that are multiples of 4*pi, those answers are all equal to 1 of course,then you multiply each by two.

What are you actually trying to do? Do you want your frequency to be 60 Hz or 60 radians per sample?

I'll assume 60 radians/sample for the moment.

    x = 0:0.001:2*pi;
    y = 2*cos(60*x);
    plot(x,y)

If you want 60 cycles per second

    x = 0:0.001:2;
    y = 2*cos(2*pi*60*x);
    plot(x,y)

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St11=100;
Sc11=St11*2/3;
St22=80;
Sc22=St22*2/3;
S=60;
i1 = 0;
r = NaN(101,51);
for phi=0:pi/50:2*pi
    i1 = i1+1;
    i2 = 0;
    if cos(phi)>=0
        X=St11;
    else
        X=Sc11;
    end
    if sin(phi)>=0
        Y=St22;
    else
        Y=Sc22;
    end
    for psi=-pi/2:pi/50:pi/2
        i2=i2+1;
        F=@(r0)(((cos(phi)*cos(psi)*r0)/X)^2-(cos(phi)*cos(psi)*r0*sin(phi)*cos(psi)*r0)/(X^2)+((sin(phi)*cos(psi)*r0)/Y)^2+(r0*sin(psi)/S)^2-1)^2;
        r(i1,i2)=abs(fminsearch(F,0));
    end
end
[psi,phi] = meshgrid(-pi/2:pi/50:pi/2,0:pi/50:2*pi);
x=cos(psi).*cos(phi).*r;
y=cos(psi).*sin(phi).*r;
z=sin(psi).*r;
surf(x,y,z)

MATLAB: (noob) Matlab Compiler Issue

The "NoClassDefFoundError" error is thrown because MATLAB is not able to locate Java Runtime libraries that are used by the MATLAB Compiler SDK.

There are several possible causes to this issue:

A. The installation is corrupted and there are .jar files missing from the MATLAB installation folder.
B. The classpath.txt file is missing references to Java Runtime libraries.

1. To take a look at the MATLAB search path, execute "pathtool" in the Command Window. This will open up the Set Path window with the list of folders that MATLAB parses. The start-up folder should be at the top.

You can try to restore the search path to the installation default by executing the following commands:

>> restoredefaultpath
>> rehash toolboxcache

However, this will not remove the start-up directory from the MATLAB search path. If the start-up folder contains M-files, try to remove them or move them to another folder which is not on the search path.

2. If the issue still persists, the installation might be corrupted. Remove MATLAB completely and install it again to resolve the issue.

Best Answer

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MATLAB: Shaded surface

MATLAB: (noob) Matlab Compiler Issue

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