Don't store these submatrices in individual variables with different names.Rather store them in a cell array.
Use histcounts to find the distribution of the indices of the rows you want to split and arrayfun or a for loop to do the splitting:
m = rand(150, 6); m(:, 4) = randi([-180 180], 150, 1); %random matrix for demo, size 150*6
[~, ~, bins] = histcounts(m(:, 4), -180:30:180);
subm = arrayfun(@(bin) m(bins == bin, :), 1:max(bins), 'UniformOutput', false)
That last line with the arrayfun is equivalent to
subm = cell(1, max(bins));
for bin = 1:max(bins)
subm{bin} = m(bins == bin, :);
end
