MATLAB: How to get the script to run properly

for loopMATLABscript

I was initially having trouble with my function, but now since that is running okay, my script is not. It involves a for loop and I'm not sure what I'm doing wrong.
Here is my function file:
function v = piecewise_fun(t)
if 0 <= t & t < 8
  v = (10.*t).^2 - (5.*t);
elseif 8 <= t & t < 16
  v = 624 - 5.*t;
elseif 16 <= t & t < 26
  v = 36.*t + 12.*(t-16).^2;
elseif t >= 26
  v = 2136*exp(-0.1.*(t-26));
end
end
And here is what I have for my script file:
t = -5:50
hold on
for i =-5:t  % I'm not sure if this is even right!?
  v = piecewise_fun(t);
end
plot(v,t)
So, I get the following error:
Undefined function or variable 'v'. Error in piecewise_plot (line 6) plot(v,t)

Best Answer

Not right. Try it this way, in an m-file called aaron.m:
function aaron
t = -5:50
for k = 1 : length(t)
  v(k) = piecewise_fun(t(k));
end
plot(t, v, 'b*-', 'LineWidth', 2);
grid on;
xlabel('t', 'FontSize', 30);
ylabel('v', 'FontSize', 30);
title('v vs. t', 'FontSize', 30);
function v = piecewise_fun(t)
v = nan; % Initialize.
if 0 <= t && t < 8
  v = (10.*t).^2 - (5.*t);
elseif 8 <= t && t < 16
  v = 624 - 5.*t;
elseif 16 <= t && t < 26
  v = 36.*t + 12.*(t-16).^2;
elseif t >= 26
  v = 2136*exp(-0.1.*(t-26));
end
Both functions are in the same m-file, called aaron.m, or whatever you want just make sure the name is on the first function line.
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