I am trying to plot some data using interp2.m and I am stuck.
I have a K*2 data set, which I wish to plot in 3D, with the 3rd dimension being the frequency of each pair of observations.
I keep getting the error message "The grid was created from grid vectors that were not strictly monotonic increasing."
This is because I am unclear on what format Z needs to be in.
my code is as follows:
K = 10000;
y = randi([1,200], [K,1]);
x = randi([1,100], [K,1]);
[C,~,ic] = unique([y x],'rows');
[z IX] = sort(histc(ic, 1:length(ic)), 'descend');
idY = (z==0);
z(idY) = [];
z = z / sum(z);
IX(idY) = [];
y=C(IX,1);
x=C(IX,2);
scatter3(x,y,z,'filled');
Now I wish to plot a mesh/surface on this data and also use interp2 for non-graphical lookups.
1. I wish to be able to plot mesh(x,y,z).
2. I wish to be able to evalaute z_1 = interp2(x,y,z,x_1,y_1, 'spline'), where x_1 and y_1 are values chosen by me.
3. Continuing from (2), if I have x_1 and wish to find the most likely value of z, how can I do this? Do i have to use a for loop and evaluate a vector of y_1 values and then take the max? or is there a better way?
How can I do this?
My attempt to make Z (as per URL) was as follows:
gridx1 = [1 : 1 : max(ceil(x))];
gridx2 = [1 : 1 : max(ceil(y))];
Z = zeros(length(gridx1), length(gridx2));
for i = 1: length(gridx1)
for j = 1: length(gridx2)
Z(i,j) = sum( (i == x) & (j == y) );
end
end
Though this doesnt work as Z is 100x200 here. I know it should be KxK. SO I try
Z = zeros(length(x), length(y));
for i = 1: length(x)
for j = 1: length(y)
Z(x(i),y(j)) = Z(x(i),y(j)) + 1;
end
end
but then I get the error I noted above.
Can anyone help? thanks !
