How to use a For loop to plot sine waves?

I need to use a for loop to plot one cycle of sine waves on the same figure and their frequencies vary from 50Hz to 250Hz with the increment of 10Hz. This is my code at the moment:

[Mathieu NOE]

hello

I don't understand the relationship between this code and a sine wave

Z looks to me like the expression of an electric impedance - BTW the capacitor term should be written 1/(2*pi*f*C)

Answer 1

[Frances McBride]

Since you did not include any errors that you are getting, I will come up with solutions based on some possible errors that you may be encountering.

1. Plotting multiple plots on the same figure

Consider using "hold." Adding the following to your function will allow you to plot multiple plots on the same figure that you defined prior to creating your forloop. https://www.mathworks.com/help/matlab/ref/hold.html

hold on
figure
for i=1:10
    f=50:i:250
    Z=sqrt(R.^2+(1/2*pi*f*C).^2);
    plot(Z,f)
end

Additionally, consider adding parentheses to the 1/2 term. You may be telling matlab to put pi in the denominator of 1/2, so be careful there.

1. The outputted plot is not a sine wave

To create a sine function, use the built-in MATLAB function sin(). This automatically calculates the sine function using radians. To use degrees, use sind(). The plot you have here is a square root curve, not a sine wave.

1. Unrecognized function or variable 'R'; unrecognized function or variable 'C'

You will get this error if you have not defined the constants in your equation for Z. If you have previously defined these constants in your script/function then you will likely not get this error. I brought this up because you didn't include where you defined R and C.

Answer 2

[Prajwal Sangalad]

hold on
figure
for i=1:10
    f=50:i:250
    Z=sqrt(R.^2+(1/2*pi*f*C).^2);
    plot(Z,f)
end

[Walter Roberson]

This will not work. You have the hold on before the figure call, so the hold is going to affect the current axes at the time of the call, creating a figure and axes if needed.

Then you call figure(), and figure by itself creates a new figure -- a figure that starts with no axes, and when the axes is created in that figure it is not going to inherit any properties from the current axes at the time of the hold call.

You need to move the figure() call to before the hold call.

[Dyuman Joshi]

Walter, @Prajwal Sangalad has just copied the code from the answer posted above by @Frances McBride.

[Walter Roberson]

Even if that were true, @Dyuman Joshi, @Prajwal Sangalad has posted an Answer to the question, and is morally responsible for dealing with responses to their Answer.