How can I index non-integer values

the code is as under: (all others are constants) I need to generate a matrix of PR of 1000 different values of R.

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PR=(1:1001);

for R=990:0.02:1010

      PR(R-989)=(pt*(g^2)*sigma*(lambda^2))/(((4*pi)^3)*R^4);    
  end

ERROR:

Attempted to access PR(1.02); index must be a positive integer or logical.

Answer 1

[Bjorn Gustavsson]

Since PR is an array it has n values at indices from 1 to n. If you want to get values at other "indices" you can turn to interpolation:

nr_you_want_out = 1001;
PRinterp = interp1(1:n,PR,linspace(1,n,nr_you_want_out));

HTH

Answer 2

[Walter Roberson]

PR=(1:1001);

Rv=990:0.02:1010;

for Ridx = 1 : length(Rv)
  R = Rv(Ridx);
  PR(Ridx)=(pt*(g^2)*sigma*(lambda^2))/(((4*pi)^3)*R^4);    
end

Alternate solution with no loop:

R = 990:0.02:1010;
PR = pt .* (g.^2) .* sigma .* (lambda.^2) ./ (4*pi).^3 ./ (R.^4);