www.pudn.com > NumericalComputingwithMatlabCode.zip > interpgui.m, change:2003-10-26,size:4049b

```function interpgui(arg1,arg2)
%INTERPGUI  Behavior of interpolating functions.
%   Demonstrates interpolation by a piecewise linear interpolant,
%   a polynomial, a spline, and a shape preserving Hermite cubic.
%   INTERPGUI(x,y) starts with a plot of y vs. x.
%   INTERPGUI(y) starts with equally spaced x's.
%   INTERPGUI(n) starts with y = zeros(1,n).
%   INTERPGUI with no arguments starts with eight zeros.
%   The interpolation points can be varied with the mouse.
%   If x is specified, it remains fixed.
%

if nargin == 0 | isnumeric(arg1)

% Interpret arguments

if nargin == 0
% interpgui with no arguments
n = 8;
x = 1:n;
y = zeros(1,n);
elseif length(arg1) == 1
% interpgui(n)
n = arg1;
x = 1:n;
y = zeros(1,n);
elseif nargin == 1
% interpgui(y)
n = length(arg1);
x = 1:n;
y = arg1(:)';
elseif length(arg1) == length(arg2)
% interpgui(x,y)
[x,k] = sort(arg1(:)');
y = arg2(k)';
else
error('Two arguments must have same length')
end
arg1 = [];

% Initialize figure

shg
clf reset
set(gcf,'doublebuffer','on', ...
'name','Interp gui', 'numbertitle','off', ...
'windowbuttondown',['interpgui(''move''); set(gcf,' ...
'''windowbuttonmotion'',''interpgui(''''move'''')'')'], ...
'windowbuttonup','set(gcf,''windowbuttonmotion'','''')');

% Initialize plots

n = length(x);
h = diff(x);
u = zeros(1,128*(n+1));
j = 1:128;
s = (1+sin((j-65)/128*pi))/2;
u(j) = x(1)+(s-1)*h(1);
for k = 1:n-1
u(128*k+j) = x(k)+s*h(k);
end
u(128*n+j) = x(n)+s*h(n-1);
p = plot(x,y,'o',u,zeros(4,length(u)),'-');
ymin = min(y);
ymax = max(y);
ydel = ymax-ymin;
if ydel == 0; ydel = 1; end
axis([min(u) max(u) ymin-0.5*ydel ymax+0.5*ydel])
title('Interpolation')

% Controls

uicontrol('units','normal','pos',[.68 .13 .12 .18], ...
'style','frame','background','white')
F = {'linear','poly','spline','pchip'};
pos = [.69 .26 .09 .04];
vis = 0;
for k = 1:4
uicontrol('units','normal','pos',pos, ...
'style','check','string',F{k},'value',vis, ...
'background','white','foreground',get(p(k+1),'color'), ...
'callback','interpgui(''cb'')');
pos(2) = pos(2)-.04;
end
uicontrol('units','normal','pos',[.85 .01 .10 .06], ...
'style','push','string','close','tag','reset/close', ...
'callback','close(gcf)');

% Remember original data

xfree = (nargin < 2);
set(gcf,'userdata',xfree)
set(gca,'userdata',{x,y})
end

p = flipud(get(gca,'children'));
x = get(p(1),'xdata');
y = get(p(1),'ydata');
n = length(x);
h = diff(x);
u = zeros(1,128*(n+1));
j = 1:128;
s = (1+sin((j-65)/128*pi))/2;
u(j) = x(1)+(s-1)*h(1);
for k = 1:n-1
u(128*k+j) = x(k)+s*h(k);
end
u(128*n+j) = x(n)+s*h(n-1);

if isequal(arg1,'reset')

% Restore original data

xy = get(gca,'userdata');
x = xy{1};
y = xy{2};
set(findobj('tag','reset/close'),'string','close', ...
'callback','close(gcf)');

elseif isequal(arg1,'move')

% Respond to mouse motion

z = get(gca,'currentpoint');
z = z(1,:);
p = flipud(get(gca,'children'));
e = abs(x-z(1));
k = min(find(e == min(e)));
xfree = get(gcf,'userdata');
if xfree
x(k) = z(1);
end
y(k) = z(2);
set(findobj('tag','reset/close'),'string','reset', ...
'callback','interpgui(''reset'')');

end

ax = axis;
set(p(1),'xdata',x,'ydata',y)
set(p(2),'xdata',u,'ydata',piecelin(x,y,u));
set(p(3),'xdata',u,'ydata',polyinterp(x,y,u));
set(p(4),'xdata',u,'ydata',splinetx(x,y,u));
set(p(5),'xdata',u,'ydata',pchiptx(x,y,u));
axis(ax);

% Visibility

b = flipud(get(gcf,'children'));
onf = {'off','on'};
for k = 1:4
% Interpolants
set(p(k+1),'visible',onf{get(b(k+2),'value')+1})
end
```