Why am I unable to display more than two legend entries for the PLOTYY function in MATLAB 7.1(R14SP3)?

I have more one data set per scale in the same PLOTYY graph. I would like to display the associated legends for each data set in the plot.

If I execute the following code:

x = 0:0.01:20;

y1 = 200*exp(-0.05*x).*sin(x);

y2 = 0.8*exp(-0.5*x).*sin(10*x);

plotyy([x,x],[y1 y1*2],x,y2)

I would like to display a legend for each data set in the plot.

Answer 1

[MathWorks Support Team]

This enhancement has been incorporated in Release 2008a (R2008a). For previous product releases, read below for any possible workarounds:

The PLOTYY function applies two axes, one overlaying the other with a transparent background. Each axes can have a legend. However, when applying the PLOTYY function in a vectorized format, for example,

plotyy([x,x],[y1 y1*2],x,y2)

the data for all of the lines on an axes is stored in one line object. Therefore, each legend cannot have more than one legend entry without generating the following warning:

 Warning: Ignoring extra legend entries.

For example:

x = 0:0.01:20;

y1 = 200*exp(-0.05*x).*sin(x);

y2 = 0.8*exp(-0.5*x).*sin(10*x);

[ax, h1, h2] = plotyy([x,x],[y1 y1*2],x,y2)

legend(ax(1), 'str1','str2');

legend(ax(2), 'str3');