Variable labels in MATLAB - matlab

Question

I have a huge table data= {1000 x 1000} of binary data.
They table's variable names are encoded for eg D1,D2,...,DA2,DA3,... with their real labels given in a .txt file.
The .txt file also consists of some text for eg:
D1: Age
Mean age: 33
Median :
.
.
.
D2: weight
I would just like to pick out these names from the text file and create a table with the real variable names.
Any suggestions?

Answer 1

If there is a specific number of lines between each of those labels, then you can extract them by reading in the file, and looping over the relevant lines. For each label, it simple to extract the label with strsplit()
e.g. Let's say there's 5 lines between each label
uselessLines = 5;
% imports as a vertical matrix with each line from the file.
dataLabelsFile = importdata(filename);
% get the total number of lines
numLines = size(dataLabelsFile);
% pre-allocate array for labels, a cell is used for a string
dataLabels = cell(ceil(numLines/(uselessLines+1)));
% use a seperate counting variable
m = 1;
% now, for each label, we add it to the dataLabels matrix
for i=1:(uselessLines+1):numLines
line = strsplit(dataLabelsFile{i}); % by default splits on whitespace
dataLabels(m) = line(2);
m = m + 1;
end
By the end of that loop you should have a variable called dataLabels that holds all of the labels. Now, you can actually very easily work out which label goes with which set of data
provided they are still in the same order. The indexes will be the same for the label to the data.
This is a method you could try if the labels are evenly spaced.
However, if the labels are a random number of lines, then you probably want to do a check with a regular expression like the person below me has suggested. Then you just replace the last two lines of the loop with something like this.
...
if (regular expression matched)
dataLabels(m) = line(2);
m = m + 1;
end
...
That being said, while regular expressions are flexible, if you can get away with replacing it with literally one function call, it's usually better to do that. Regex efficiencies are determined by the skill of the programmer, while in-built functions have generally been tested by some of the better programmers in the world. Additionally, Regex's are harder to understand if you ever want to go back and change it.
Of course there are times when Regex's are amazing, I'm just not convinced this is one of those times.

Answer 2

An implemention of the approach in my earlier comment:
fid = fopen(filename);
varNames = cell(0);
proceed = true;
while proceed
line = fgetl(fid);
if ischar(line)
startIdx = regexp(line,'(?<=^[A-Z]*\d*:)\s');
if ~isempty(startIdx)
varNames{end+1} = strtrim(line(startIdx:end)); %#ok<SAGROW>
end
else
proceed = false;
end
end
fclose(fid);
I cant put the resulting varNames in a table for you, since I have a version of Matlab that does not support tables.