creating an equal lateral triangle in matrix

12 views (last 30 days)
Is there an easy method for generating an equal lateral triangle centered and the middle of a matrix? The image attached is what I want the matrix to look like except the triangle would be made of 1s and the background zero. Thank you in advanced.

Answers (2)

jonas
jonas on 10 Nov 2018
Edited: jonas on 10 Nov 2018
You could do something like this:
poly = polyshape([1 2 1.5],[1 1 2])
plot(poly)
set(gca,'xcolor','none','ycolor','none')
F = getframe(gca)
I = imbinarize(rgb2gray(F.cdata))
imshow(~I)
change coordinates of the polygon to create your desired triangle.
  1 Comment
John D'Errico
John D'Errico on 10 Nov 2018
Drat. Polyshape has not been around long enough that I think of it immediately. :)

Sign in to comment.


John D'Errico
John D'Errico on 10 Nov 2018
Any number of ways, certainly many if I spent any amount of time to think them up. Simplest?
1. Start with meshgrid, creating sets of indices into the final array.
2. Create a polygon, that denotes the corners of the triangle.
3. Use inpolygon to indicate which points lie inside the triangle.
4. Assign the array initially uing zeros.
5. Use logical indexing to overwrite the points inside the polygon as 1.
So simple and fast, fully vectorized. But many other ways too.

Categories

Find more on Elementary Polygons in Help Center and File Exchange

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by