How do I get regexp to read specific values in a text file?

I am currently having a problem in using regular expression to extract numbers from a text file.

This is a part of a file I am working on:

---------------------------------------------------------------------

Center Atomic Atomic Coordinates (Angstroms)

Number Number Type X Y Z

---------------------------------------------------------------------

1 8 0 0.000000 -0.000000 0.114681

2 1 0 -0.000000 0.754069 -0.458726

3 1 0 -0.000000 -0.754069 -0.458726

---------------------------------------------------------------------

Rotational constants (GHZ): 858.6604959 440.9403948 291.3341325

Standard basis: 6-31G(d) (6D, 7F)

There are 10 symmetry adapted cartesian basis functions of A1 symmetry.

There are 1 symmetry adapted cartesian basis functions of A2 symmetry.

There are 3 symmetry adapted cartesian basis functions of B1 symmetry.

There are 5 symmetry adapted cartesian basis functions of B2 symmetry.

There are 10 symmetry adapted basis functions of A1 symmetry.

There are 1 symmetry adapted basis functions of A2 symmetry.

I am trying to get 3 numbers from the line starting with "Rotational constants (GHZ):".

This is my attempt:

content = fileread('myFile.txt');

pattern = 'Rotational constants (GHZ):\s*(\d+\.\d+)\s*(\d+\.\d+)\s*(\d+\.\d+)';

tokens = regexp(content, pattern, 'tokens);

values = sscanf(tokens{1}{1}, '%f');

The error I am getting is I keep getting empty array for my tokens. Based on this error, I think my regular expression is uncorrect. However, I am not exactly sure how to fix it.

Thanks

Answer 1

[Abhilash Padma]

The pattern you are using involves special characters ‘(’ and ‘)’. You should use ‘\’ before special characters in pattern. The pattern should be “(?<=Rotational constants \(GHZ\):\s+)(\d+\.\d+)\s*(\d+\.\d+)\s*(\d+\.\d+)” .