plot a nonlinear function matlab

Question

I'm very new to Matlab and have problem plotting this nonlinear 2D function graph using Matlab.

a lot of errors generated after the below is run.

fun1 =  20 + 10 + 15;
fun2 =  20 + (x * 0.00125 ) + 15;
fun3 = (x * 0.0025) + 15;

fplot(fun1,[0 8000])
fplot(fun2,[8000 16000])
fplot(fun2,[16000 positive infinity])

I appreciate a lot to your efforts and kindness for replying my question Best Regards

Daniel · Accepted Answer · 2013-12-10 17:47:08Z

1

Your first three expressions do not define functions. Please read the documentation about the correct syntax.

fun1 = @(x)(20 + 10 + 15);

answered Dec 10, 2013 at 17:47

Daniel

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Chris Taylor · Accepted Answer · 2013-12-10 17:47:00Z

0

First create a file fun.m which contains your function definition

function y = fun(x)
  if x < 8000
    y = 20 + 10 + 15;
  elseif x < 16000
    y = 20 + (x * 0.00125) + 15;
  else
    y = x * 0.0025 + 15;
  end
end

Then you can plot it with

fplot(@fun, [0 24000])

which results in

enter image description here

answered Dec 10, 2013 at 17:47

Chris Taylor

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Comments

mhmsa · Accepted Answer · 2013-12-10 17:50:39Z

0

If you do some reading in fplot you will find out that for fplot(fun,limits) fun must be

The name of a function
A string with variable x that may be passed to eval, such as 'sin(x)', 'diric(x,10)', or '[sin(x),cos(x)]'
A function handle

so in your case you need to change all of you fun to strings just add ' before and after the expression

as for the last line change it to be

fplot(fun2,[16000 inf])

although i don't think this would give you any good results

answered Dec 10, 2013 at 17:50

mhmsa

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