Plotting an array on both x and y axis and different formulas, check description

i want to plot a graph in a such a way, that some of values undergo a same formula while other values undergo a different formula. In my case i m drawing a shear force diagram for a beam, it has length of 10m, i divided the interval i = 0:0.1:7 and j = 7:0.1:3 For first interval a formula will be applied lets say y = 2*i and for second part y= 3*i and a graph is to be plotted with i on x-axis and y on y-axis

[Awais Saeed]

j = 7:0.1:3 seems a typo mistake.

Answer 1

[Chunru]

 i = 0:0.1:7;
 j = 7:0.1:10;
 yi = 2*i;
 yj = 3*j;
 plot(i, yi);
 hold on
 plot(j, yj)