MATLAB Answers

Why can i not plot this?

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Emil Cramer
Emil Cramer on 28 Oct 2015
Answered: Thorsten on 28 Oct 2015
i run this script clc
close
clear
%input%
Q=0.034;
T=0.0454;
S=0.0014;
t=365*24*60*60;
%equation%
for x=1:1:10;
y=(2.30*Q)/(4*pi*T)* log10((2.25*T)/(x.^2*S))+ (2.30*Q)/((4*pi*T))*log10(t);
end
plot(x,y)
but it does not show the plot on the figure

Answers (2)

Rob Campbell
Rob Campbell on 28 Oct 2015
Edited: Rob Campbell on 28 Oct 2015
You can't plot anything because your code is full of mistakes. For starters, x and y are both just one number so you don't have an series of data points to plot. The loop is wrong. Your code is also very difficult to read and badly laid out and this is contributing to your confusion. If you correct those things, you will have an easier time figuring out what's wrong. Do the following:
1. Store your code in a .m file (ideally as a function: http://uk.mathworks.com/help/matlab/ref/function.html) and run that file.
2. Don't cram too much stuff on each line. One statement per line. Look at the code examples in the MATLAB docs and emulate that style.
3. Don't start with "clear". Blindly clearing the workspace isn't desirable and if you use a function then the variables are all local to it and will never need cleaning like this anyway.

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Thorsten
Thorsten on 28 Oct 2015
You don't need the for loop, but you have use ./ before (x.^2*S)):
x = 1:10; % no need to use :1:, 1 is the default increment
y=(2.30*Q)/(4*pi*T)* log10((2.25*T)./(x.^2*S))+ (2.30*Q)/((4*pi*T))*log10(t);
plot(x,y)

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