CODEWITHSUNDEEP
regexmatlab
shashashamti2008
shashashamti2008

Reputation: 2327

Issue with a regular expression

How can I write a regular expression to return the value of the mesh volume? The file containing this information is printed below.

Mesh Bounding Box Size 13119.671875  13057.258789  5996.836426
Mesh Bounding Box Diag 19457.128906 
Mesh Bounding Box min -6823.634277  -6530.717773  0.000000
Mesh Bounding Box max 6296.037598  6526.541016  5996.836426
Mesh Surface Area is 373208000.000000
Mesh Volume  is 48660.9190912000000
Mesh Total Len of 2430 Edges is 1946449.875000 Avg Len 801.008179
Mesh Total Len of 2430 Edges is 1946449.875000 Avg Len 801.008179 (including faux edges))
Thin shell (faces) barycenter:  -228.323471  -0.174702  1865.262939
Vertices barycenter  -175.590256   7.494401  2809.697754

I am able to get the volume of the mesh (which is 48660.9190912000000) using the following:

\d+[.]*\d+$

but it also matches all the other numbers. I tried 

(Mesh Volume  is)\w+\d+[.]*\d+$

but it fails to find any match. Could someone help me with that?

If I group the numbering as the following, can I return the value of the volume as \1?

(Mesh Volume  is)\w+(\d+[.]*\d+)$

My goal is to find a working regular expression to use in MATLAB regexp function.

Upvotes: 2

Views: 82

Answers (3)

Luis Mendo
Luis Mendo

Reputation: 112679

You can use lookbehind as follows. Note also that

  • The decimal point is \., not .
  • I'm using your original regular expression as a base. It would fail for negative numbers, or if there are no digits before the decimal point.

Code in Matlab:

s = 'Mesh Surface Area is 373208000.000000 Mesh Volume  is 48660.9190912000000'; % example
result = regexp(s, '(?<=Mesh Volume  is )\d+\.?\d+', 'match');

Upvotes: 1

tim
tim

Reputation: 492

You could try something like this:

%float_pattern = "[0-9.]+";
float_pattern = "\d+(?:\.\d+)?";
pattern = "Mesh Volume  is (?<MeshVolume>" + float_pattern + ")";

matches = regexp(information, pattern, 'match')
tokens = regexp(information, pattern, 'tokens')
names = regexp(information, pattern, 'names')

if isfield(names, "MeshVolume")
    fprintf("Mesh Volume = %f m^3\n", names.MeshVolume);
else
    fprintf("Failed to find mesh volume.\n");
end

Upvotes: 2

The fourth bird
The fourth bird

Reputation: 163362

If you want to grab the number, you could use the capturing group for the number instead of the text.

For your example data, you can omit \w+ as the number directly follows is.

Note that the pattern you tried \d+[.]*\d+$ might also match 1..1. When there is no dot it requires at least 2 digits due to the two times \d+.

You could use:

Mesh Volume  is (\d+(?:\.\d+)?)

Explanation

  • Mesh Volume is Match literally
  • ( Capture group 1
    • \d+ Match 1+ digits
    • (?:\.\d+)? Optionally ? match a single dot followed by 1+ digits
  • ) Close group 1

Regex demo

Upvotes: 2

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