Counting the occurrence of a value=Inf in an array

I am given a vector for instance

R=[1;2;3;4;5;6 Inf; 7; Inf];

Is there a function in matlab which has inputs R and Inf and gives me back the number of occurrence of Inf in R?

Answer 1

[Paras Gupta]

Hi,

It is my understanding that you need a function to find the total number of 'Inf' values in a given array. Though there does not seem to be any one particular function to find the same, you can very easily find the solution using two functions as is illustrated in the following code.

R = [1; 2; 3; 4; 5; 6; Inf; 7; Inf];

% isinf returns a logical array with true (1) at indices where element is inf
% nnz returns the number of non-zero values in the array 
infCount1 = nnz(isinf(R))

infCount1 = 2

% one could also use sum function instead of nnz
infCount2 = sum(isinf(R))

infCount2 = 2

You can refer to the following documentations on isinf, nnz, and sum for more information on how the above code works.

Hope it helps!

[Steven Lord]

isinf may or may not be the right tool, depending on whether the user wants all infinite values in the array to be counted or just the positive ones.

% Sample data: Inf for multiples of 3, -Inf for multiples of 5, NaN for both
x = (1:15).';
x(3:3:end) = Inf;
x(5:5:end) = -Inf;
x(15) = NaN;

allInf = isinf(x);
justPositive = x == Inf;
nonfinites = ~isfinite(x);
results = table(x, allInf, justPositive, nonfinites)

results = 15×4 table
     x      allInf    justPositive    nonfinites
    ____    ______    ____________    __________

       1    false        false          false   
       2    false        false          false   
     Inf    true         true           true    
       4    false        false          false   
    -Inf    true         false          true    
     Inf    true         true           true    
       7    false        false          false   
       8    false        false          false   
     Inf    true         true           true    
    -Inf    true         false          true    
      11    false        false          false   
     Inf    true         true           true    
      13    false        false          false   
      14    false        false          false   
     NaN    false        false          true