how to generate random isotropic vectors using R?

Matlab rotation using vectors and sin/cos?

• Hi, I was assigned a project to draw two rectangles using plot lines and rotating them by creating vectors for the x and y values using the variables on the rectangle using sin and cos. I have already plotted the lines but the rotation is not showing up, I'm not sure what is missing. clear all close all clc x1=2; y1=3; x2=5; y2=3; x3=2; y3=3.4; x4=5; y4=3.4; X1=5; Y1=3; X2=8; Y2=3; X3=5; Y3=3.4; X4=8; Y4=3.4; axis([0,10,0,10]); hold on; xlabel('x-axis'); ylabel('y-axis'); %rectangle one plot ([x1,x2],[y1,y2]); plot ([x1,x3],[y1,y3]); plot ([x3,x4],[y3,y4]); plot ([x4,x2],[y4,y2]); %rectangle two plot ([X1,X2],[Y1,Y2]); plot ([X1,X3],[Y1,Y3]); plot ([X3,X4],[Y3,Y4]); plot ([X4,X2],[Y4,Y2]); %rotation theta=30; x=[2;5;3;5]; y=[3;3;3.4;3.4]; xrot= x.*cosd(theta)+y.*sind(theta); yrot= -x.*sind(theta)+y.*cosd(theta); plot= [xrot,yrot];

• Answer:

  There are a couple errors I see. Your x vector (x = [2;5;3;5]) is incorrect. As defined earlier the points are 2,5,2,5. You should order the points by walking along each edge of the rectangle. Starting from the bottom left, the first rectangles x values are 2,5,5,2,2. There is a fifth value to account for returning to the rectangles origin. Another error is that you are creating a plot variable to hold xrot and yrot. It should be the plot function, not plot =. I find it redundant to create that x vector holding each x value for rotation, and in the beginning creating 4 x variables. Matlab Code: clear all close all clc rx1 = [2,5,5,2,2]; ry1 = [3,3,3.4,3.4,3]; rx2 = [5,8,8,5,5]; ry2 = [3,3,3.4,3.4,3]; axis([0,10,0,10]); hold on; xlabel('x-axis'); ylabel('y-axis'); %rectangle one plot (rx1,ry1); %rectangle two plot (rx2,ry2); %rotation theta=30; xrot= rx1.*cosd(theta)+ry1.*sind(theta); yrot= -rx1.*sind(theta)+ry1.*cosd(theta); plot(xrot,yrot,'r'); hold off;