Plot control signals in Matlab from Simulink

Hi there! My work in simulink contains the following parts. Blocks: 1 "constant", 2 1-D lookup tables, 3 scopes where one of them works as a control signal and finally 1 display. And the main purpose is to control the levels in two water containers in a water tank. Moving on to my question.

It says in my description that the control signal and scope value have been saved in the workspace in shapes of matrices.(so far so good) And the first column corresponds to time and the second one is the value of the signal. "You pick one column out of a matrix by typing the name (variable) followed by (:,n) were n is the columns number."

Task: "In the command window, make a new plot with number 3 and plot the control signal by typing plot(u(:,1),u(:,2)). Press on the magnifying glass and make a square around the step in the curve. Zoom in further to decide the exact time the step was made." Ok so in Simulink, then I made the step by changing the "constant"-value from 1.45 V to 1.65 V, but when I´m about to plot the control signal, all I see is a flat line, no curve at all! No step no nothing! -_- What am I doing wrong here?

[Shivaputra Narke]

Is there any snaps of the issue. ?

[René Gothe]

snaps? ... I should say that I´m not that skilled yet! x) Have been working in Matlab/Simulink for like 2 weeks.