How to write/design a matrix similar to the one outputted by contourf

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sparsh garg 2021-9-21

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评论： sparsh garg 2021-9-21

So the output of contourf is a matrix of 2xN dimension as described here

Contour matrix, returned as two-row matrix. This matrix contains the contour levels (heights) and the coordinates of the vertices at each level. The data is arranged sequentially in n sets of columns for n contour lines:

The first column in each set contains the contour level and the number of vertices at that level. The top number is the contour level, and the bottom number is the number of vertices.
Subsequent columns in the set are the (x, y) coordinates of the vertices. Each column represents an ordered pair. The top number is the x-coordinate, and the bottom number is the y-coordinate.

Now let's say that I have a set of points ,I would like to organize them in a similar manner described above

for example let's say i have 1200 points

i want matrix to look like this

[first column] S.no 1 no of points 500

then 501st column S no 2 no of points 400

and finally 901 column S no 3 no of points 300

Would a strucutre or a class be better suited.

the class can have a method which retrieves the desired no of points for the particular S no

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sparsh garg 2021-9-21

编辑：sparsh garg 2021-9-21

R_stroke_pts.mat

The input of the problem is as follows

the below image is a subsection of the R.

What I am doing here is ,I want to fit a circle whose center is denoted by the black circle and the radius is the distance between the black point and the purple point.

[the black point is the mid point of the line that connects one point on the top curve and one point on the bottom curve]

Now if I was to just take the first four black point and fit a circle with respect to those points,I end up with four circles.

so let's say you have C1,C2 ,C3,and C4.Each of these is a 2xN matrix then currently i am returning an overall concatenation of C1 ,C2 ,C3 and C4 whose dimensions are 2X2142.

My expected output;

a structure/some data struicutre which tells me how many circles are there,for each circle how many points are there and what are those points.

The closest is the contour matrix returned by contourf which tells us for a particular level how many points are there.

For example,when I ran contourf on the enclosed matrix for level 110. the output M matrix looks like this

first column [level 110 9 points] and then you have 9 columsn corresponding to the x y values.

enclosed is the R 's xy plot.note this is not the actual R image(which I cannot share)

Adam Danz 2021-9-21

编辑：Adam Danz 2021-9-21

Instead of concatenating the 2xN coordinates along the second dimension, if N is equal for all circles, then I would concatenate them along the 3rd dimension using cat(3,___). If N is not equal for all circles, I would store each set of coordinates in a 1xN or Nx1 cell array.

Note that your description differs from the contour output in that your data are coordinates whereas the contour output contains level and number-of-verticies which is does not intuitively provide coordinate information.

sparsh garg 2021-9-21

yes i think that might work,i will try it .

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