How can I define a variable Y as a function of another variable X, where the first function (Y) changes over a specific range of the dependent variable (X)?

Hello,

I am trying to define two variables (YTF and YAF) in ways that vary by the range of the variable 'AGE':

AGE = 20:1:65;

syms YTF if ge(50-AGE,0), YTF = 50-AGE;, else YTF = 0;, end

syms YAF if ge(65-AGE,15), YAF = 15;, else YAF = 65-AGE;, end

But when I do this, MatLab seems to recognize 'AGE' as the value '65'. The result is that 'YAF' is a '46x251 Double', but 'YTF' is a single value of 0.

I need MatLab to recognize neither YTF nor YAF as a single value, since I'll be using YAF and YTF in various equations.

Thanks for any advice.

Answer 1

[Star Strider]

There’s no reason to use the Symbolic Math Toolbox for this. It is straightforward to use anonymous functions:

AGE = 20:1:65;

YTF = @(AGE) ((50-AGE) >= 0).*(50-AGE);
YAF = @(AGE) ((65-AGE) >= 15).*15 + ((65-AGE) < 15).*(65-AGE);

figure(1)
subplot(2,1,1)
plot(AGE, YTF(AGE), 'LineWidth',1.5)
ylabel('YTF')
grid
subplot(2,1,2)
plot(AGE, YAF(AGE), 'LineWidth',1.5)
ylabel('YAF')
xlabel('AGE')
grid