The cumtrapz function integrates a vector, and ideally, the dependent variable vector with respect to the independent variable vector.
The limits of the independent variable vector are the limits of the integration, so for example:
x = 0:42;
y = randn(size(x));
Int_y_dx = cumtrapz(x, y);
figure
yyaxis left
plot(x, y)
ylabel('$y(x)$', 'Interpreter','latex')
yyaxis right
plot(x, Int_y_dx)
ylabel(sprintf('$\\int_{%d}^{%d}y(x)\\ dx$',min(x),max(x)), 'Interpreter','latex', 'FontSize',14)
grid
xlim([min(x) max(x)])
.
