Polarplot axis label: how to edit the value?

Expert,

Can anyone tell me how is it possible to change the radial axis label in polarplot function? I want the original label to be subtracted by certain value, e.g. 1.0

I just to manipulate the axis label, without changing the value of the data or result. Thus, the plot will essential remain the same, just the label is "manipulated".

Suppose I have the following data:

x = linspace(0,2*pi);
y = cos(x)+ sin(x);

polarplot(x,y)

The results of that function is

Now, what I want is to change the original axis label [0 0.5 1.0 1.5] into [-1 -0.5 0 0.5].

How can we do that?

This is what I expect

Answer 1

[dpb]

hPP=polarplot(x,y);            % plot, save handle
hPA=hPP.Parent;                % retrieve polar axes handle (parent of polar plot)
hPA.RTickLabel=hPA.RTick-1;    % rewrite radius tick labels as desired
hPA.RColor='r';                % change color

[BeeTiaw]

Thanks @dpq

More question:

• How is it possible to remove the first label? i.e. the -1?
• How to control the number of label displayed in the polar plot?

[madhan ravi]

rticks([0.5 1.0 1.5])
rticklabels([-0.5 0 0.5])

[BeeTiaw]

Hi Madhan Ravi, this can only be done if the label is known.

What I am after is for a general case, i.e. I don't have any prior information about the label. So, how to ignore just the first element of the label?

[dpb]

As with all other axes, the tick labels can be set independently of the tick values as far as content but there must be a tick at any given location to label. For the first to just not display one, you simply

Rlab=hPA.RTickLabel;     % retrieve existing tick labels
Rlab{1}='';              % clear the one don't want
hPA.RTickLabel=Rlab;     % and rewrite

NB: the size of the tick label array must match the size of the tick array or the labels will either not all be displayed (longer) or the elements will be repeated as needed to label all ticks (shorter).

Second question is combination of the above, depending on the effect you're after -- more ticks means set the .RTick property to have the number/spacing you wish; to leave the number the same but the number of displayed labels is the first (note you can this way only have the same number or fewer labels than ticks; you can't have more labels than ticks).

Read the documentation on axes and axes properties for more details...

[BeeTiaw]

Thanks again dpb,

But this line:

Rlab{1} = ' ';

in the code gives me error. It says "unable to perform assignment because brace indexing is not supported for variables of this type"

How can I fix this?

[dpb]

Dunno...what type is Rlab on your system? It's a cell array here with ML R2017b so that works just peachy-keen...

>> hP=polarplot(x,y);
>> hPA=hP.Parent;
>> Rlab=hPA.RTickLabel;
>> whos Rlab
  Name      Size            Bytes  Class    Attributes

  Rlab      4x1               464  cell               

>> Rlab{1}=''
Rlab =
  4×1 cell array
    {0×0 char}
    {'0.5'   }
    {'1'     }
    {'1.5'   }
>> 

What do you see different there and which release of ML you running?

[BeeTiaw]

Rlab is char in my case

whos Rlab
  Name      Size            Bytes  Class    Attributes

  Rlab      3x4                24  char              
  
  >> Rlab

Rlab =

  3×4 char array

    '-1  '
    '-0.5'
    '0   '

[BeeTiaw]

It works fine now after converting the char into cell into your original code:

hP=polarplot(x,y);
hPA=hP.Parent;
Rlab=hPA.RTickLabel;
Rlabstr = cellstr(Rlab);
Rlabstr{1}='';              % clear the one don't want
hPA.RTickLabel=Rlabstr;     % and rewrite

Thank you for your kind help dpb!

The code gives me what I want now.

[dpb]

What release of ML???

I've never seen the dot notation return a char array in such a use--is that really the exact code? That's bizzaro, if so.

I think you'd already cleared the first row elements before by the output shown because it's

>> whos Rlab
  Name      Size            Bytes  Class    Attributes
  Rlab      3x4                24  char              
  
>>

and is already 3x4 instead of 4x4 elements as it would be if hadn't already eliminated the first element. I think you inadvertently must have done something else to have caused the conversion from cell array to char array.

I just reran the sample here and even after clearing the first label content in the cell array and rewriting, as expected if one retrieves the new 'RTickLabel' content, it's still a cell array of four elements.

[Cesim Dumlu]

@dpb Thanks for the answer. Is it possible to modify the fontsize of rticks only ?

[dpb]

No, 'FontSize' is only one property for the polar axes object -- follow the links from the "See Also" link to the section on properties for the object -- or save the axes handle and click on the "show all properties" link that shows up in the command window if you display the handle value interactively.