How can I set an axis outside the polar figure like this photo?

Hello friends,

I want to add a scalebar of my r-axis and label it like the figure I show (with red ring), but it seem not easy to move the exsisting axis, what should I do?

Can anyone help me? I really appreciate it.

Answer 1

[Tommy]

You could create Cartesian axes which overlie the polar axes and are invisible except for the y axis, whose ticks are set to match the r axis ticks:

pa = polaraxes('Position', [0.25 0.25 0.6 0.6]);
polarplot(pa, randi(10,10,1),'o');
pa.RTickLabel = [];

a = axes('Color', 'none',...
    'XColor', 'none',...
    'Position', pa.Position,...
    'YLim', [-pa.RLim(2) pa.RLim(2)],...
    'YTick', unique([-flip(pa.RTick) pa.RTick]));
ylabel(a, 'r axis label')

[Hengkai Wu]

Oh yeah, I really appreciate it for your answer, and sorry for my slow acception.

There is still a small question. I want to make the axis tick increase in both two directions, like the figure shows, (a to 0 to a) rather than ( -a to 0 to a). How can I achieve this? Should I set a new axis and reverse it? Or in other ways?

Can you tell me? Thanks. XD

[Tommy]

Oh of course! Not sure how I overlooked that... You could specify the tick labels:

pa = polaraxes('Position', [0.25 0.25 0.6 0.6]);
polarplot(pa, randi(10,10,1),'o');
pa.RTickLabel = [];
ticks = [-flip(pa.RTick(2:end)) pa.RTick];
a = axes('Color', 'none',...
    'XColor', 'none',...
    'Position', pa.Position,...
    'YLim', [-pa.RLim(2) pa.RLim(2)],...
    'YTick', ticks,...
    'YTickLabel', abs(ticks));
ylabel(a, 'r axis label')

[Hengkai Wu]

Thanks for your help. XD

Answer 2

[zein]

how can i modify the rlabel to be starting from 70 instread of zero as i have used the same code but for my case i want the scale to start from 70 instead of zero as shown in the following figure

I have used the same code line but the output rlabel started from zero

what should i modify in the code to set the rlabel from (70-120)

figure(2)
set(gcf,'color','w');
ax = polaraxes('Position', [0.25 0.25 0.6 0.6])
polarplot (theta,splbn(21,:));
ax.ThetaDir = 'counterclockwise';
ax.ThetaZeroLocation = 'left';
rlim([70,120])

ax.RTickLabel = [];
ticks = [-flip(ax.RTick(2:end)) ax.RTick];

a = axes('Color', 'none',...
    'XColor', 'none',...
    'Position', ax.Position,...
    'YLim', [-ax.RLim(2) ax.RLim(2)],...
    'YTick', ticks,...
    'YTickLabel', abs(ticks));
ylabel(a, 'r axis label')

[Tommy]

Hello, try this:

figure(2)
set(gcf,'color','w');
ax = polaraxes('Position', [0.25 0.25 0.6 0.6]);
polarplot (theta,splbn(21,:));
ax.ThetaDir = 'counterclockwise';
ax.ThetaZeroLocation = 'left';
ax.RTickLabel = [];

% grab the tick locations before changing the r limits, because the
% tick locations should be centered around 0:
ticklocs = [-flip(ax.RTick(2:end)) ax.RTick];

rlim(ax, [70,120])
ticks = [-flip(ax.RTick(2:end)) ax.RTick];

a = axes('Color', 'none',...
    'XColor', 'none',...
    'Position', ax.Position,...
    'YLim', [min(ticklocs), max(ticklocs)],...
    'YTick', ticklocs,... use the tick locations to place the ticks
    'YTickLabel', abs(ticks));
ylabel(a, 'r axis label')

Hopefully this works for you