通常，當要顯示的數據的範圍較大時，通常會將數據的某個局部細節就無法仔細觀察，這個時候，如果能夠放大某個局部，那麼將會非常好。下圖是筆者在MathWorks上面看到的一個很棒的帶有數據局部放大窗口功能的工具箱。
官方給出的工具箱實現代碼如下：
function MagInset(h, ax, ZoomArea, InsetPos, Lines)
% ************ MagInset.m *************
% * Created: January 1, 2015 *
% * By: Damien Frost *
% * Inspiration By: Robert Richardson *
% *************************************
%
% MagInset (Magnified Inset) places an axes inset into an existing
% figure with handle h. Re-size your figure and axes before running
% MagInset.
%
% h - handle to a figure on which to place an inset
%
% ax - handle to an axes object. Set to -1 to use the default axes in the
% figure.
%
% ZoomArea - a 4x1 array which defines the zoom area that inset
% should have. It is of the form:
% [xmin xmax ymin ymax]
% The values are NOT normalized values, but graph values. In
% this way, you can easily read off the zoom area you would like
% to specify.
%
% InsetPos - defines the position of the inset. It is of the form:
% [xmin xmax ymin ymax]
% The values are NOT normalized values, but graph values. In
% this way, you can easily read off the inset area you would
% like to specify
%
% Lines - defines a list of lines to connect the zoom area with the inset
% graph. It can be empty. It should be of the form:
% Lines = {'NW','SW'; 'NE','SE'};
% It can have as many rows as you wish
% The first colum is the corner of the Zoom Area. The second column is the
% corner of the Inset Axes
BadInput = 0;
axesObjs = get(h, 'Children'); %axes handles
% Determine which axes the inset will be placed on:
if(ax == -1)
MainAx = axesObjs(end);
else
MainAx = -1;
for ii=1:1:max(size(axesObjs))
if(axesObjs(ii) == ax)
MainAx = axesObjs(ii);
break;
end
end
if(MainAx == -1)
% Could not find the desired axes:
fprintf('\nMagInset Error: Could not find the desired axes in the figure.\n');
BadInput = 1;
end
end
if(BadInput == 0)
% Get the plot data:
dataObjs = get(MainAx, 'Children');
% Annotation positions are of the form:
% [x y length height]
% And are normalized to the figure
% Calculate the normalize rectangular coordinates for the zoom area:
[zax, zay] = xy2norm(MainAx, ZoomArea(1:2), ZoomArea(3:4));
% Create the rectangle around the area we are going to zoom into:
annotation('rectangle',[zax(1) zay(1) (zax(2) - zax(1)) (zay(2) - zay(1))]);
% Calculate the inset position in normalized coordinates;
[ipx, ipy] = xy2norm(MainAx, InsetPos(1:2), InsetPos(3:4));
if(nargin > 4)
% Add the lines from the zoom area to the inset:
numLine = size(Lines,1);
if((numLine>0) && (size(Lines,2) == 2))
lx = zeros(2,1);
ly = zeros(2,1);
for ii=1:1:numLine
jj = 1;
% Find the co-ordinate in the zoom area:
% y co-ordinates:
if(Lines{ii,jj}(1) == 'S')
ly(jj) = zay(1);
else
ly(jj) = zay(2);
end
% x co-ordinates:
if(Lines{ii,jj}(2) == 'W')
lx(jj) = zax(1);
else
lx(jj) = zax(2);
end
jj = 2;
% Find the co-ordinate in the inset axes:
% y co-ordinates:
if(Lines{ii,jj}(1) == 'S')
ly(jj) = ipy(1);
else
ly(jj) = ipy(2);
end
% x co-ordinates:
if(Lines{ii,jj}(2) == 'W')
lx(jj) = ipx(1);
else
lx(jj) = ipx(2);
end
% Add the line:
annotation('line', lx,ly);
end
end
end
% Add the second set of axes on the same plot:
iaxes = axes('position', [ipx(1) ipy(1) (ipx(2) - ipx(1)) (ipy(2) - ipy(1))]);
hold on;
box on;
% Add the plots from the original axes onto the inset axes:
copyobj(dataObjs,iaxes);
% set the limits on the new axes:
xlim(ZoomArea(1:2));
ylim(ZoomArea(3:4));
% Our work here is done.
end
end
function [xn, yn] = xy2norm(axh, x, y)
% ********* xy2norm.m *********
% * Created: January 1, 2015 *
% * By: Damien Frost *
% *****************************
% This function takes a point (x, y) and returns the normalized
% co-ordinates (xn, yn) given the axes with handle axh.
%
% *** Modifications: ***
% 1) Added 'axh = handle(axh);' line to make the script backwards
% compatible with MATLAB R2013a (Perhaps further back) - Thanks Shi
% Zhao!
axh = handle(axh);
% Save some temporary variables about the axes:
axPos = axh.Position;
xlims = axh.XLim;
ylims = axh.YLim;
% Calculate the normalized co-ordinates:
xn = axPos(1) + axPos(3) .* (x-xlims(1))./(xlims(2) - xlims(1));
yn = axPos(2) + axPos(4) .* (y-ylims(1))./(ylims(2) - ylims(1));
% GTFO:
end
要畫出上面兩幅圖片的效果，可以使用如下的兩個腳本實現：
% An example of how to use MagInset.m
clear all;
% **************************************
% * Example 1: Single axes on a figure *
% **************************************
% Create a figure with a sine wave with random noise on it:
h1 = figure;
title('Single Axes MagInset Example');
hold on;
f0 = 10000;
t = 0:(1/f0)/1000:((1/f0)*2);
y = 5*sin(2*pi*f0*t) + rand(size(t));
plot(t*1000, y);
grid on;
xlabel('Time (ms)');
ylabel('Amplitude (V)');
% It is important to set the figure size and limits BEFORE running
% MagInset!
xlim([t(1) t(end)]*1000);
ylim([-6 10]);
% Once happy with your figure, add an inset:
MagInset(h1, -1, [0.04 0.045 1 4], [0.05 0.09 5.5 9], {'NW','NW';'SE','SE'});
% ****************************************
% * Example 2: Multiple axes in a figure *
% ****************************************
% Create a figure with a sine and cosine wave with random noise on it:
h2 = figure;
% Sine Wave:
ax(1) = subplot(2,1,1);
title(sprintf('MagInset Example with Subplots\n'));
hold on;
f0 = 10000;
t = 0:(1/f0)/1000:((1/f0)*2);
y = 5*sin(2*pi*f0*t) + rand(size(t));
plot(t*1000, y);
grid on;
xlabel('Time (ms)');
ylabel('Amplitude (V)');
xlim([t(1) t(end)]*1000);
ylim([-6 10]);
% Cosine Wave:
ax(2) = subplot(2,1,2);
hold on;
y = 5*cos(2*pi*f0*t) + rand(size(t));
plot(t*1000, y,'r');
grid on;
xlabel('Time (ms)');
ylabel('Amplitude (V)');
xlim([t(1) t(end)]*1000);
ylim([-6 10]);
% Link the x axes:
linkaxes(ax,'x');
% Once happy with your figure, add an inset:
% Cosine inset:
MagInset(h2, ax(1), [0.04 0.045 1 4], [0.05 0.09 5.5 9], {'NW','NW';'SE','SE'});
% Sine insets:
MagInset(h2, ax(2), [0.015 0.02 1.5 4], [0.038 0.078 5.5 9], {'NW','NW';'SE','SE'});
MagInset(h2, ax(2), [0.18 0.185 1.5 4], [0.125 0.165 5.5 9], {'NE','NE';'SW','SW'});