xline issue with adding a number to the line through the labels option

Is there a reason why the xline (or yline) functions won't accept a number converted to a string

c=b(3);   %Breakpoint
cs=num2str(c)
class(cs)
xline(ax3,c,cs);

cs =
'125.7048'

ans =
'char'

Error using xline
Invalid parameter/value pair arguments.

Answer 1

[Aditya]

Hi Jason,

In MATLAB, the xline function is designed to add vertical lines to a plot and allows for customization through various parameters, including adding a label directly to the line. However, this customization needs to be done using 'Name,Value' pairs. When you attempt to pass the string representation of a number directly as an argument, without specifying it as part of a 'Name,Value' pair, MATLAB does not recognize it as a valid input, leading to the "Invalid parameter/value pair arguments" error.

To add a label to your line correctly, you need to use the 'Label' option followed by the string you wish to use as the label. Here's how you can adjust your code:

% Correct way to add Label 
xline(ax3,c,'Label',cs);

I hope this clears up the confusion!

[Jason]

That did it thanks.

The online manual doesnt' actualyl say this and gives this example

x = linspace(0,6,100);
y = exp(x);
plot(x,y)
xline(4.5,'-',{'Acceptable','Limit'});

[Jason]

and to further add, reading again it says this:

To create a line with a label, you must also specify the line style. The default line style is a solid line, '-'.

x = linspace(0,6,100);
y = exp(x);
plot(x,y)
xline(4.5,'-',{'Acceptable','Limit'});

So it is possible without the 'Label' but you need to specify the line stsyle, so actually this worked also.

xline(ax3,c,'-',cs);

[Aditya]

yes, you can specify the label this way:

xline(ax3,c,'-',cs);

You can also specify the linestyle: Specify Line and Marker Appearance in Plots - MATLAB & Simulink - MathWorks India