% Worshop Example 4 (WorkshopEx04.m)
%
% This script evaluates a file that specifies a truss.
% It does this by defining the following two matrices
% 
% nodes - an nn-by-2 matrix with one row per node, where
%         each row specifies the (x,y) coordinates of the
%         corresponding node
%
% bars  - an nb-by-2 matrix with one row per bar, where
%         each row specifies the indices of the source and 
%         target nodes for the corresponding bar.
%
% The script then plots the specified truss

% Daniel D. Warner
% July 9, 2008

name = input('Enter the name of the file defining the truss: ','s');
eval(name)

% Plot the nodes as black cicles
[nn,two] = size(nodes);
xn = nodes(:,1);
yn = nodes(:,2);
plot(xn,yn,'ok')

title(name)
% Set the view, include a small margin around the truss 
xmargin = 0.1*max(abs(xn));
ymargin = 0.1*max(abs(yn));
xmin = min(xn) - xmargin;
xmax = max(xn) + xmargin;
ymin = min(yn) - ymargin;
ymax = max(yn) + ymargin;
axis([xmin xmax ymin ymax]);

% Plot the bars
hold on
[nb,two] = size(bars);
for k=1:nb
    % Get the index for the first node (source node) of bar k
    sindx = bars(k,1);
    % Get the index for the second node (target node) of bar k
    tindx = bars(k,2);
    plot([xn(sindx) xn(tindx)],[yn(sindx) yn(tindx)])
end

% label the nodes
xoffset = xmargin/4;
yoffset = ymargin/4;
for k=1:nn
    text(xn(k)+xoffset, yn(k)+yoffset, num2str(k))
end
hold off