Plotting points and lines

I have two arrays, one with points, and one of members saying which points they wish to connect. Below is the data. So essentially there is supposed to be points at (node_x,node_y). Then I would like to connect those points with 21 members ie size(member_nodes). For example, the first member should connect nodes 2 and 3 which are at points (0,0) and (5,0) respectively. Also if possible, it would be optimal to label what member/node is what on the plot. Thanks in advance, I realize this is a bit complicated.

node_x = [15.0, 0.0, 5.0, 10.0, 15.0, 20.0, 25.0, 30.0,  5.0, 10.0,  20.0, 25.0].';
node_y = [5.0 , 0.0, 0.0,  0.0,  0.0,  0.0,  0.0,  0.0,  5.0,  5.0,   5.0,  5.0].';

      member_nodes = [2, 3;
                      3, 4;
                      4, 5;
                      5, 6;
                      6, 7;
                      7, 8;
                      2, 9
                      3, 9;
                      3, 10;
                      4, 10;
                      4, 1;
                      5, 1;
                      1, 6;
                      6, 11;
                      11, 7;
                      7, 12;
                      12, 8;
                      9, 10;
                      10, 1;
                      1, 11;
                      11, 12];

Answer 1

[Walter Roberson]

x_coords = [node_x(member_nodes), NaN(size(member_nodes,1),1)];
y_coords = [node_y(member_nodes), NaN(size(member_nodes,1),1)];
plot(x_coords(:), y_coords(:))

[alex]

thanks for the fast reponse...

however this isn't exactly giving me what I want. it was very close but it was wrong for a couple of the members. I tried switching the order of the nodes of those trouble members around and it just got worse. if you plot it and get it working it is a symmetrical bridge. could you give it another look?

[alex]

to be specific its missing two and showing three incorrectly.

[alex]

Even after simplifying to this I get the same plot. I've check and rechecked my nodes/members countless times and it still plots it incorrectly. To be specific it's members 7-11 that are incorrect.

x_coords = [node_x(member_nodes)];

y_coords = [node_y(member_nodes)];

plot(x_coords(:), y_coords(:))

[Walter Roberson]

You will have an incorrect graph if you left out the NaN().

[alex]

its incorrect with the NaN() and its exactly the same without it...

[alex]

changing the order of the member_nodes in fact changes the plot greatly. Are you sure there is no way to avoid this problem?

[Walter Roberson]

Sorry I glanced at this at work but didn't see anything obvious. I do not have access to MATLAB from home.

[Walter Roberson]

alex, it looks like gplot() would help you.

http://www.mathworks.com/help/techdoc/ref/gplot.html

In your case, the adjacency matrix would be

accumarray(member_nodes, 1)