MWE_bold

y = zeros(1, 1000);
x = 1:1000;
n = length(x);

figure
plot(x, y)

% without math env
tit_norm = sprintf('\\textbf{This curve has n = %d points}', n);

% with math env
tit_math = [sprintf('\\textbf{This curve has '), ...
            sprintf('$\\mathbf{n=%d}$', n), ...
            sprintf(' points}')];

title(tit_math, 'interpreter', 'latex')