Extracting numbers from a txt file

I am struggling to extract all the numbers i need to out of a .txt file.

The file goes

# File created = Thursday, June 16, 2022 2:47:40 PM BST
# Data set = "testdata"  515  1  "C:\Users\ben\data"
# Spectral Region:
# F1LEFT = 13.912019729614258 ppm. F1RIGHT = -13.912050717676049 ppm.
# F2LEFT = 32.79998016357422 ppm. F2RIGHT = -17.17222595626548 ppm.
#
# NROWS = 512 ( = number of points along the F1 axis)
# NCOLS = 2048 ( = number of points along the F2 axis)
#
# In the following ordering is from the 'left' to the 'right' limits!
# Lines beginning with '#' must be considered as comment lines.
#
# row = 0
163.60546875
.
.
.

The ... is the other 512*2048 numbers.

raw = 'testdata.txt';
raw = readmatrix(raw);
Y = zeros(512,2048);
for i = 1:512
    blockstart =2048*(i-1)+i;
    blockend = 2048+blockstart-1;
    Y(i,:) = raw(blockstart:blockend,1);
end

I currently use the above code to extract the long number chain into the rows and columns it should be. However, i dont know how to extract F1LEFT/RIGHT or F2LEFT/RIGHT or the values for NROWS/NCOLS. Currently i manually type them into their corresponding variable in my code. I tried the route of using strfind and extracting them like that but i couldnt get it to work. Any suggestions?

Answer 1

[Karim]

If the header will always use the same structure, you can try something like the code below.

Hope it helps, best regards

% link to the text file
fileID = fopen('Example.txt'); 
% read the whole file, interpret each line as a string
MyText = textscan(fileID, '%s%[^\n\r]', 'Delimiter', '', 'WhiteSpace', '',  'ReturnOnError', false);
% convert the cell array into a string array, for easier indexing
MyText = string(strtrim(MyText{1}));

% Get specific data
currLine = contains(MyText, "F1LEFT");
currLine = split(MyText(currLine),' ');

F1LEFT = str2double( currLine(4) )

F1LEFT = 13.9120

F1RIGHT = str2double( currLine(8) )

F1RIGHT = -13.9121

currLine = contains(MyText, "F2LEFT");
currLine = split(MyText(currLine),' ');

F2LEFT = str2double( currLine(4) )

F2LEFT = 32.8000

F2RIGHT = str2double( currLine(8) )

F2RIGHT = -17.1722

currLine = contains(MyText, "NROWS");
currLine = split(MyText(currLine),' ');

NROWS = str2double( currLine(4) )

NROWS = 512

currLine = contains(MyText, "NCOLS");
currLine = split(MyText(currLine),' ');

NCOLS = str2double( currLine(4) )

NCOLS = 2048

% now get the data
raw = readmatrix('Example.txt');
raw = reshape(raw,NROWS,NCOLS);

size(raw)

ans = 1×2

512 2048

[Ben Smith]

Ahh thank you. Because it comes from an outside program it will always come in the same form so this works perfectly.