matlab中pchip,MATLAB中chckxy函数

鄙人在网上找了许久找不到pchip中关于chckxy函数的相关知识，在matlab命令窗口使用edit

chckxy也打不开该函数，后查资料发现这是一个private函数，也许跟这个有关系吧~现贴出该函数具体内容供参考：

function [x,y,sizey,endslopes] = chckxy(x,y)

%CHCKXY check and adjust input for SPLINE and PCHIP

% [X,Y,SIZEY] = CHCKXY(X,Y)

checks the data sites X and corresponding data

% values Y, making certain that

there are exactly as many sites as values,

% that no two data sites are

the same, removing any data points that involve

% NaNs, reordering the sites if

necessary to ensure that X is a strictly

% increasing row vector and

reordering the data values correspondingly,

% and reshaping Y if necessary

to make sure that it is a matrix, with Y(:,j)

% the data value corresponding

to the data site X(j), and with SIZEY the

% actual dimensions of the

given values.

% This call to CHCKXY is

suitable for PCHIP.

%

% [X,Y,SIZEY,ENDSLOPES] =

CHCKXY(X,Y) also considers the possibility that

% there are two more data

values than there are data sites.

% If there are, then the first

and the last data value are removed from Y

% and returned separately as

ENDSLOPES. Otherwise, an empty ENDSLOPES is

% returned. This call to CHCKXY is suitable for SPLINE.

%

% See also PCHIP, SPLINE.

% Copyright 1984-2011 The

MathWorks, Inc.

% make sure X is a vector:

if length(find(size(x)>1))>1

error(message('MATLAB:chckxy:XNotVector'))

end

% ensure X is real

if any(~isreal(x))

error(message('MATLAB:chckxy:XComplex'))

end

% deal with NaN's among the sites:

nanx = find(isnan(x));

if ~isempty(nanx)

x(nanx) = [];

warning(message('MATLAB:chckxy:nan'))

end

n=length(x);

if n<2

error(message('MATLAB:chckxy:NotEnoughPts'))

end

% re-sort, if needed, to ensure strictly increasing site

sequence:

x=x(:).';

dx = diff(x);

if any(dx<0), [x,ind] = sort(x); dx = diff(x); else ind=1:n;

end

if ~all(dx), error(message('MATLAB:chckxy:RepeatedSites')),

end

% if Y is ND, reshape it to a matrix by combining all dimensions

but the last:

sizey = size(y);

while length(sizey)>2&&sizey(end)==1, sizey(end) = [];

end

yn = sizey(end);

sizey(end)=[];

yd = prod(sizey);

if length(sizey)>1

y = reshape(y,yd,yn);

else

% if Y happens to be a column

matrix, change it to the expected row matrix.

if yn==1

yn = yd;

y = reshape(y,1,yn);

yd = 1;

sizey = yd;

end

end

% determine whether not-a-knot or clamped end conditions are to

be used:

nstart = n+length(nanx);

if yn==nstart

endslopes = [];

elseif nargout==4&&yn==nstart+2

endslopes = y(:,[1 n+2]);

y(:,[1 n+2])=[];

if any(isnan(endslopes))

error(message('MATLAB:chckxy:EndslopeNaN'))

end

if any(isinf(endslopes))

error(message('MATLAB:chckxy:EndslopeInf'))

end

else

error(message('MATLAB:chckxy:NumSitesMismatchValues',nstart,

yn))

end

% deal with NaN's among the values:

if ~isempty(nanx)

y(:,nanx) =

[];

end

y=y(:,ind);

nany = find(sum(isnan(y),1));

if ~isempty(nany)

y(:,nany) = []; x(nany) =

[];

warning(message('MATLAB:chckxy:IgnoreNaN'))

n = length(x);

if n<2

error(message('MATLAB:chckxy:NotEnoughPts'))

end

end

今天就先贴个代码，以后有时间给你们慢慢翻译~~

其实在pchip文件中，在chckxy函数上右键打开或者Ctrl+D就能打开该函数了哦~~