This should be easy (i hope), create area using coordinates

Hi all,

I am new to MATLAB and creating a particle tracking model combined to a hydrodynamic model. I initially start by using a square utilizing xMIN xMAX, yMIN, yMAX. However, I have imported the Coordinates from a shape file from arcMAP 10.1 using a .txt file. My question is how can I possibly define the starting position of the particles within the boundaries of the area of the coordinates. i.e if i joined the dots together how do i put the particles within this area and give them a random position within this area.

heres the code upto the release point and random positon within the grid

%%gets the grid and bathymetry, only need it once                      
folder = 'U:\College of Natural Sciences\Research Data\mar1990\'; 
depthandgrid = ([folder,'mar90.00001.nc']);         % Select file
ncid = netcdf.open(depthandgrid,'NC_NOWRITE');      % Opens file
depth = netcdf.getVar(ncid,0,'double');             % Depth
landsea = netcdf.getVar(ncid,1,'double');           % Border between land and sea
netcdf.close(ncid);                                 % Closes netcdf

%%Irish Sea and POM variables
X1 = -9.0; X2 = -2.7;        % X-axis
Y1 = 50.1; Y2 = 56.;         % Y-axis
xspac = 1/30;                % X-axis grid distances
yspac = 1/60;                % Y-axis grid distances
long = X1: xspac: X2;        % Long = x axis
lati = Y1: yspac: y2         % Lati = y axis 
nt   = 10272;                % Number of time steps
nx = 190; ny = 354; nz = 21; % Irish sea grid dimensions
dt = 1800;                   % POM output time step
dx = 2000.; dy = 2000.;      % Cell size (m)
start = 4000;                % Starting iteration
finish = 4200;               % Finishing iteration
np = 1000;                   % Number of particles released 

%%Initial example release site:
xSMNRmin = 115*dx; xSMNRmax = 125*dx; ySMNRmin = 125*dy; ySMNRmax = 135*dy; zSMNRmin= 21; zSMNRmax = 21; % Gives  start points in metres

%Loops for all particles to give a random position
for i=1:np;                                          
  x(i)=(rand*(xSMNRmax-xSMNRmin))+xSMNRmin;   % Random place in the grid with the x direction
  y(i)=(rand*(ySMNRmax-ySMNRmin))+ySMNRmin;   % Random place in the grid with the y direction

thanks Hayden

[Sara]

Do you mean that the coordinates you import from the shapefile do not describe a rectangle box, so you need a way to determine if a point is within an area of arbitrary shape?

[Image Analyst]

What's wrong with using rand() like you did? It looks fine to me (other than missing the end statement).