# union of polyshapes, problem with collinearity

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Hello,
I have 15 polygons (of streets) that I can merge into one using the union function.
But if I want to unite only a few of them (that are close to each other), I get:
Error using polyshape/parseCollinear (line 946)
Parameter name must be 'KeepCollinearPoints'.
Error in polyshape/parseIntersectUnionArgs (line 973)
collinear =
polyshape.parseCollinear(varargin{next_inp:end});
Error in polyshape/union (line 42)
[has_clip, collinear] = polyshape.parseIntersectUnionArgs(false,
varargin{:});
Unfortunately, I don't really understand what MatLAB wants me to do to get my unified polygon groups.
Ah, and if polygons are collinear, I'd like to keep those collinear points.
Thank you!
##### 2 CommentsShowHide 1 older comment
Alexandra Kopaleyshvili on 23 May 2021
never done this before, hope it works

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### Accepted Answer

Matt J on 23 May 2021
Edited: Matt J on 23 May 2021
You just had a comma separated list in there by accident. The polyshapes must be given to union() as a vector.
load(websave('t','https://www.mathworks.com/matlabcentral/answers/uploaded_files/627388/streets_185.mat'));
A=union([Streetshape_185.L2{1,1}{:,1}],'KeepCollinearPoints',true)
A =
polyshape with properties: Vertices: [3604×2 double] NumRegions: 3 NumHoles: 0
plot(A)
##### 1 CommentShowHide None
Alexandra Kopaleyshvili on 23 May 2021
sometimes it's so easy. thank you so much!:)

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