Issue with && in matrix operation.

Hi, i have a problem with the && operators, which it cannot operate the following code:

i = noTier1 + 1;
while i ~= (numNodes + 1)
  x = round((area_length - 1) * (rand(10,1) - 0) / (1 - 0) + 1);
  y = round((area_width - 1) * (rand(10,1) - 0) / (1 - 0) + 1);
  % measure distance between x,y and base station
  A = squareform( pdist([x - baseStation.x, y - baseStation.y]) );
  A(A > edges) = 0;
  if A > tier1Radius && A < tier2Radius
    node(i).x = x;
    node(i).y = y;
    node(i).energy = 1;
    node(i).id = i;
    node(i).tier = 2;
    node(i).pch = 0;
    node(i).sch = 0;
    node(i).residual = 1;
    node(i).centrality = rand;
    node(i).commCost = 0;  
    i = i + 1;
  end
end

The error:

Operands to the || and && operators must be convertible to logical scalar values.

Error in MAPmm (line 94)
     if A > tier1Radius && A < tier2Radius

Here the input

A = carry matrix value. 
noTier1 = 25;
numNodes = 100;
area_length = 100;
area_width = area_length;
baseStation.x = 50;
baseStation.y = 50;
tier1Radius = 25;
tier2Radius = 50;

How can i solve this problem, pls advice me.

Thanks sir.

[dpb]

You're mixing array and element operations; you need to either use logical addressing for all elements from the logic expression or iterate over the array A element-by-element; can't mix both.

Not at all clear what the i loop is iterating over beginning at 25+1 but the A array will be one-based.

As the error says, you need for the specific line

if A(i)>tier1Radius & A(i)<tier2Radius

and iterate of A, but that needs a different loop variable than the i you've got over the elements of A.

[Asyran Abdullah]

Already try use single &, also got error. Then i try this:

if   A < tier2Radius | A > tier1Radius

It run smoothly.

[Walter Roberson]

You just set some A locations to a value, and then you want to test if they ALL satisfy the condition?

Your squareform pdist is returning a 2d array, not a scalar.

[Asyran Abdullah]

Yes, then how can 2d array perform a logical scalar values?

Answer 1

[the cyclist]

I suggest that you carefully read the documentation for these "short-circuit" logical operators. They do not operate on vectors -- only scalars.

I'm not sure what you expect they will do, so I'm not sure what to recommend as a replacement. If you describe what you intend, someone can probably help.

[Walter Roberson]

It would, for example, help if there was a response to https://www.mathworks.com/matlabcentral/answers/421474-how-to-perform-arithmetic-operation-in-pdist#comment_616298

[Asyran Abdullah]

Ok sir,

1. Actually what i want to do is to distribute random node in 100x100 area.

      x = round((area_length - 1) * (rand(15,1) - 0) / (1 - 0) + 1);
      y = round((area_width - 1) * (rand(15,1) - 0) / (1 - 0) + 1);

2. Then each of the points/nodes will connect as multihop into each other. Which the last blue nodes connect to nearest purple nodes.

3. Then i want to insert some "weights/cost/metric" to each path in order to calculate the shortest path among others.

path = shortestpath(G,1,14);

4. The process will be done in two-tier of network as follow:

However, the blue nodes cannot connect to each other and it difficult to do a shortest path. I hope someone can give a suggestion and advices.

Thanks

Answer 2

[Walter Roberson]

You can change the && to &

However remember that there is an implicit all() when testing in if or while so you would be testing whether the condition held for ALL members of A.