Plot the phase plane

I am trying to plot the phase plane.

The code gives the error :Undefined function or variable 'ciplot'.

Error in phaseplane1 (line 6)
        ciplot(lower, upper, x, 'b')

I tried to define ciplot as a function by using the code:

function ciplot(lower,upper,x,colour);

if nargin<4
colour='b';
end

if nargin<3
    x=0:0.01:2;
end

But it still doesn't work.

Answer 1

[Walter Roberson]

http://www.mathworks.com/matlabcentral/fileexchange/13103-plot-confidence-intervals ciplot is in the File Exchange

[LALE ASIK]

Thank you so much.