why X and Y coordinates must have the same size ?

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Reema Alhassan 2018-6-26

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https://ww2.mathworks.cn/matlabcentral/answers/407432-why-x-and-y-coordinates-must-have-the-same-size

评论： Walter Roberson 2018-6-28

hello,

I have an image and a shape and I need to clip the image based on the coordinates of the shape but when I do this I am having an error says: x and y must be the same size how can I make them equal? or any idea of solving this issue please ?

Thanks

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Reema Alhassan 2018-6-26

编辑：Reema Alhassan 2018-6-26

在 MATLAB Online 中打开

image001 3.png

the image is very large I can't attach it here I have attached the error that I'm having and here is the code :

info = geotiffinfo('SVDNB_npp_20121201-20121231_75N060W_vcmcfg_v10_c201601041440.avg_rade9h.tif');
%disp(info);
[x1,y1]= pixcenters(info);
%pix2map(info.RefMatrix,1,1)
shape = shaperead(fullfile('KTAF_sat_shapefiles','shapefiles','SAU0.csv.shp'));
x2=shape.X;
y2=shape.Y;
%numel(x)
%numel(y)
[x3,y3]= polyclip(x1,y1,x2,y2,1);
function [X,Y] = polyclip(x1,y1,x2,y2,method) % POLYCLIP  Clip two polygons (intersect, union, xor, diff).
%
%  [X,Y] = POLYCLIP(X1,Y1,X2,Y2,METHOD) clips the two polygons given by the %  points (X1(i),Y1(i)) and (X2(j),Y2(j)) according to the METHOD:
%         METHOD = 0 or 'dif' ==> difference (P1-P2)
%         METHOD = 1 or 'int' ==> intersection
%         METHOD = 2 or 'xor' ==> Xor
%         METHOD = 3 or 'uni' ==> Union
%  X and Y are cell arrays (because the result may be multiple polygons) %  containing the x and y coordinates of the resulting polygon(s).
%
%  XY = POLYCLIP([X1 Y1],[X2 Y2],METHOD) does the same assuming the Xi and Yi %  are column vectors.  The result is {X Y}.
%
% See also CLIPPER, POLYOUT.
% Copyright (c)2015-17, Prof. Erik A. Johnson <JohnsonE@usc.edu>, 01/29/17
% 09/13/15  EAJ  Initial code
% 01/28/17  EAJ  Update for newer MATLAB versions % 01/29/17  EAJ  Fix: test for METHOD as string, single output
narginchk(2,5);
if any(nargin==[2 4]), method=[]; end
if any(nargin==[2 3]) % POLYCLIP([X1 Y1],[X2 Y2],METHOD)
    if size(x1,2)~=2 || size(y1,2)~=2 || ~isnumeric(x1) || ~isnumeric(y1),
        error('The [X1 Y1] and [X2 Y2] matrices must be numeric two-column matrices.');
    end
    if nargin == 3
        method = x2;
    else
        method = [];
    end
    y2=y1(:,2); x2=y1(:,1);
    y1=x1(:,2); x1=x1(:,1);
else
    if ~isnumeric(x1) || ~isnumeric(y1) || ~isnumeric(x2) || ~isnumeric(y2)
        error('The polygon coordinates must be numeric matrices.')
    elseif numel(x1)~=length(x1) || numel(y1)~=length(y1) || numel(x2)~=length(x2) || numel(y2)~=length(y2)
        error('Function only handles the clipping of one polygon with another, not multiple polygons with multiple polygons');
    elseif numel(x1)~=numel(y1) || numel(x2)~=numel(y2)
        error('X1 must be the same size as Y1, and X2 the same size as Y2.');
    end;
    if length(x1)==numel(x1), x1=x1(:); y1=y1(:); end; % ensure column
    if length(x2)==numel(x2), x2=x2(:); y2=y2(:); end; % ensure column
    if nargin == 4
        method = [];
   end
end;
if isempty(method), method=0; end
if isstr(method)
    find(lower(method(1))==['dixu']) - 1;
    if isempty(ans)
        error('METHOD must be an integer (0 to 3) or {''diff'',''int'',''xor'',''union''}.');
    end;
    method = ans;
end
if ~isscalar(method) || ~any(method==0:3)
    error('METHOD must be 0, 1, 2 or 3.')
end;
scale = 2^32;
% leave this in array format just in case we later adapt this
pack   = @(p) arrayfun(@(x) struct('x', int64(x.x*scale),'y', int64(x.y*scale)),p);
unpack = @(p) arrayfun(@(x) struct('x',double(x.x)/scale,'y',double(x.y)/scale),p);
poly1 = struct('x',num2cell(x1,1),'y',num2cell(y1,1));
poly2 = struct('x',num2cell(x2,1),'y',num2cell(y2,1));
assert(numel(poly1)==1, 'Only single polygon clippings are allowed in the current code');
poly3 = unpack(clipper(pack(poly1),pack(poly2),method));
if isempty(poly3)
    x = cell(1,0);
    y = cell(1,0);
else
    x = {poly3.x};
    y = {poly3.y};
end
% % package into single polygon with NaN's separating individual polygons % lens = cellfun(@numel,{poly3.x}'); % cellfun(@(x,l) [x;NaN(max(lens)-l,1)], {poly3.x}', num2cell(lens), 'UniformOutput',false); x=cat(2,ans{:}); % cellfun(@(y,l) [y;NaN(max(lens)-l,1)], {poly3.y}', num2cell(lens), 'UniformOutput',false); y=cat(2,ans{:});
if nargout>=2
    X = x;
    Y = y;
else
    % X = cellfun(@(x,y) [x(:) y(:)],x,y,'UniformOutput',false);
    X = {x y};
end
end

Reema Alhassan 2018-6-26

编辑：Reema Alhassan 2018-6-26

yes,this is the error

Walter Roberson 2018-6-26

在 MATLAB Online 中打开

What shows up for

size(x1)
size(y1)
size(x2)
size(y2)

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Answer 1

Walter Roberson 2018-6-26

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/407432-why-x-and-y-coordinates-must-have-the-same-size#answer_326299

I suggest using poly2mask() to create mask (binary image) that you can then multiply by the original image to get the clipped image. You might always want find the bounding box of the mask and use that to crop the result.

Your x and y coordinates will need to be the same length for poly2mask.

That might involve deliberately repeating some coordinates. For example to express y ranging from 10 to 20 at x = 7, coming from (0,0), then you cannot just code x = [0 7], y = [0 10 20] -- each y must be matched with an x. You would instead code x = [0 7 7], y = [0 10 20]

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Reema Alhassan 2018-6-28

my problem is that the geotiff image is very large so I need to clip it first based on the boundingBox of the shape to make it smaller and then apply the function inpolygon() but I couldn't find a way to clip it and make a new geotiff image if you know how to do this could you help me please?

Thanks

Walter Roberson 2018-6-28

"Expecting input number 1, X, to be finite"

is an error you are getting because you are feeding in a polygon that has NaN inside it, to mark the end of a segment such as to move over to draw a lake or island. You need to break up your inputs to poly2mask, creating several masks and or'ing them together.

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why X and Y coordinates must have the same size ?

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