# My plot comes up as a white graph with no line.

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Yunus Mercan on 12 Apr 2021
Commented: Image Analyst on 12 Apr 2021
When I try to plot with this code which is given below, nothing comes up. There are no errors, there's just a blank page. I want to lines between y values depending t values.
clear all;
clc;
for t=1:25
if t==1,2,3,4,5;
y(t) = 1
elseif t==6,7,8,9,10;
y(t) = 0.9
elseif t==11,12,13,14,15,;
y(t) = 1
elseif t==16,17,18,19,20,;
y(t) = 1.05
elseif t==21,22,23,24,25,;
y(t) = 1
end
end
figure
hold on;plot(t, y)
xlabel('t(1/100)'); ylabel('VR');
title('VR Değişimi'); Expected graph is like that Stephen23 on 12 Apr 2021
Edited: Stephen23 on 12 Apr 2021
The basic problem is that this syntax
if t==1,2,3,4,5;
is equivalent to writing this (i.e. each expression is evaluated independently):
if t==1
2
3
4
5;
That is not the correct way to compare mulitple values at once. Remember that the name MATLAB comes from MATrix LABoratory: you should always keep your data in vectors/matrices/arrays. For example:
if any(t==[1,2,3,4,5])
% ^^^^^^^^^^^ vector!
Note that you should preallocate y before the loop:
Note that whilst it is certainly possible to plot vertical lines, your approach will not do this.
Image Analyst on 12 Apr 2021
Instead of an if/else, a switch statement can be used to compare multiple cases at a time. For example:
switch(result)
case 1
disp('result is 1')
case {52, 78}
disp('result is 52 or 78')
end

Atsushi Ueno on 12 Apr 2021
1. After exexuting your script, y is like [1 0 0 0 0 0.9 0 0 0 0 1 ....] it must be different from what you expected.
2. After executinf for loop, the variable t is going to be deleted. So, you need t = 1:25 after the for loop.
clear all;
clc;
t = 1:25;
y = repelem([1 0.9 1 1.05 1], 1, 5);
figure
hold on;
plot(t, y)
xlabel('t(1/100)');
ylabel('VR');
title('VR Değişimi');
Yunus Mercan on 12 Apr 2021
Atsushi Ueno,It works fine this time, thank you for your interest.

Jithin Nambiar J on 12 Apr 2021
Edited: Jithin Nambiar J on 12 Apr 2021
Your code can get pretty long and tedious. The if statement in your code would not work well because it wont compare the values separated by commas properly.
t=0.0001:0.01:40;
x=[t>0]-0.05.*[t>5]+0.05.*[t>15]+0.05.*[t>25]-0.05.*[t>35];
plot(t,x)
grid on;
xlabel('t(1/100)'); ylabel('VR');
title('VR Değişimi');
Unless you plan to plot another graph in the same above plot. You don't need to use
hold on
Hope this helps. Cheers! Yunus Mercan on 12 Apr 2021
Thank you Jithin Nambiar J,It works fine.