While Loop problems

I am trying to write a while loop. I want to read a matrix first, once ive done this i want to ask the user for co-ordinates, if those co-ordinates lie outside the matrix i want to display "these co-ordinates dont lie within the mining area" since the matrix displays a mine.

Once a suitable set of co-ordinates within the matrix is established i then want to ensure that the value in the matrix selected is zero, should the value not be zero i want to ask the user for a new set of co-ordinates.

Here's what i have so far,i feel like i lmost have it worked out however i just cant get the last part to work.

dirt_grid = csvread('dirtgrid.csv');

for base_station_x = input('Enter an x co-ordinate for the base station: ' );
    if base_station_x > length (dirt_grid)
       disp('The x co-ordinate is outside the mining area, please enter another co-ordinate')
        base_station_x = input('Enter an x co-ordinate for the base station: ' );
  end
end

for base_station_y = input('Enter an y co-ordinate for the base station: ' );
   while base_station_y > length (dirt_grid)
        disp('The y co-ordinate outside mining area, please enter another co-ordinate')
        base_station_y = input('Enter an y co-ordinate for the base station: ' );
    end
end

base_station = dirt_grid (base_station_x, base_station_y);
    while base_station >= 1
        disp('The location you have entered is not a valid location')
    end

I am aware that this program forms a infinite loop but im not sure where i should place this last loop to make the problem work. Thanks for any assistance anyone is able to provide...

Answer 1

[Teja Muppirala]

This is one way to go about doing it. (x is from left to right, and y is from top to bottom.)

dirt_grid =[  0     1     1     0     1
              1     1     0     0     1
              1     1     1     0     0];
base_location_is_zero = false;
while ~base_location_is_zero
      try
          isok = 0;
          while ~isok
              base_station_x = input('Enter an x co-ordinate for the base station: ' );
              if ~ismember(base_station_x, 1:size(dirt_grid,2))
                  disp('The x co-ordinate is outside the mining area, please enter another co-ordinate')
              else
                  isok = 1;
              end
          end;
          isok = 0;
          while ~isok
              base_station_y = input('Enter an y co-ordinate for the base station: ' );
              if ~ismember(base_station_y, 1:size(dirt_grid,1))
                  disp('The y co-ordinate is outside the mining area, please enter another co-ordinate')
              else
                  isok = 1;
              end
          end;
          base_station = dirt_grid (base_station_y, base_station_x);
          if base_station ~= 0
              disp('The location you have entered is not a valid location')
          else
              base_location_is_zero = true;
          end
      catch
          disp('Bad input. Put in an integer and try again.')
      end
end;
disp('Everything is ok!');