Use regular expression to extract a matrix from a file

Dear all,

I've been trying to read a matrix from a (very confusing) file, as shown below.

I am using MATLAB R2017a and the textread function with '%f%f%f%f' to read the "$Nodes" to "$EndNodes" numbers, but I had no success. What is the correct mask format to read this file as I need? More precisely, I need to extract the matrix from [1 0 0 0] to [12 0.3939339828220179 0.6060660171779821 0] in this example.

$MeshFormat
2.2 0 8
$EndMeshFormat
$Nodes
24
1 0 0 0
2 1 0 0
3 1 1 0
4 0 1 0
5 0.35 0.5 0
6 0.65 0.5 0
7 0.5 0.35 0
8 0.5 0.65 0
9 0.3939339828220177 0.393933982822018 0
10 0.6060660171779819 0.3939339828220176 0
11 0.6060660171779821 0.6060660171779821 0
12 0.3939339828220179 0.6060660171779821 0
$EndNodes
$Elements
46
1 1 2 3 1 1 2
2 1 2 4 2 2 3
3 1 2 5 3 3 4
4 1 2 4 4 4 1
5 2 2 1 1 6 20 17
6 2 2 1 1 7 15 13
7 2 2 1 1 9 14 15
$EndElements

Answer 1

[dpb]

>> fid=fopen('gabe.txt');
>> a=cell2mat(textscan(fid,repmat('%f',1,4),'headerlines',5,'collectoutput',1))
a =
    1.0000         0         0         0
    2.0000    1.0000         0         0
    3.0000    1.0000    1.0000         0
    4.0000         0    1.0000         0
    5.0000    0.3500    0.5000         0
    6.0000    0.6500    0.5000         0
    7.0000    0.5000    0.3500         0
    8.0000    0.5000    0.6500         0
    9.0000    0.3939    0.3939         0
   10.0000    0.6061    0.3939         0
   11.0000    0.6061    0.6061         0
   12.0000    0.3939    0.6061         0
>> fid=fclose(fid);

If you don't know where the first record of interest is, you can find it...

fid=fopen('gabe.txt');
while isempty(strfind(fgetl(fid),'$Nodes')),end
a=cell2mat(textscan(fid,repmat('%f',1,4),'headerlines',1,'collectoutput',1));