How to load numeric & string data from .txt file

5 次查看（过去 30 天）
Petrus
Petrus 2012-10-17
评论： Luca Parziale 2022-6-30
Dear all,
It might be a regular and common topic but I am unable to fix this issue properly.
Starting from a .txt file (let's say data.txt):
data_name1 data_name2 data_name3
0 OK 0,1,2
1 NOK 0,2.05E-05,8.5
Goal is to have in matlab workspace:
data_name1 = [ 0 ; 1 ]
data_name2 = {'OK','NOK'}
data_name3 = [ 0 1 2 ; 0 2.05E-05 8.5]
I tried readtext.m from file exchange but take huge amount of time and need lots of specific treatment afterward. Using eval also increased processing time of my function. Note: I have no specific toolbox apart from simulink.
Thanks in advance,
Pierre
  1 个评论
Luca Parziale
Luca Parziale 2022-6-30
Hi, maybe my code can help you. It's not better than Matt Kindig but it may inspire you :
% load .txt data into string vector
PC = readlines("pouvoir_calorifique_brute_moyen.txt");
PC = split(PC); % separate at each space to create an string array with column
PC = replace(PC,"_"," ") % now change the multi-words names
labelx = PC(1,2);
labely = PC(1,3);
l = length(PC);
PC_kg = PC(2:l, 2); PC_kg = str2double(PC_kg);
PC_m3 = PC(2:l, 3); PC_m3 = str2double(PC_m3);
labels = PC(2:l, 1);

请先登录，再进行评论。

请先登录，再回答此问题。

采纳的回答

Matt Kindig
Matt Kindig 2012-10-17
编辑：Matt Kindig 2012-10-17
This should do it, for your specific case:
fid = fopen('data.txt', 'rt');
C = textscan(fid, '%d %s %f,%f,%f', 'HeaderLines', 1, 'CollectOutput', true);
fclose(fid);
data_name1 = C{1};
data_name2 = C{2};
data_name3 = C{3};
  3 个评论
显示 1更早的评论
Matt Kindig
Matt Kindig 2012-10-17
编辑：Matt Kindig 2012-10-17
Hmm, so that makes it substantially trickier. How large is the file? If you can read it into Matlab all at once, you might be able to use regular expressions to do this. I don't have time right now to code up a full solution, but this sample code should get you started.
EDIT: Found a better way, updated code to minimize eval() statements.
str = fileread('data.txt'); %read entire file into string
parts = strtrim(regexp( str, '(\r|\n)+', 'split')); %split by each line
columns = strtrim( regexp(parts{1}, '\s+', 'split')); %columns
ncol = length(columns); %number of columns
parts(1)= []; %remove column headers
nrows = length(parts); %number of rows
M = cell( nrows, ncol); %pre-allocate empty cell array for data
%now loop through parts
for k=1:nrows,
data = strtrim(regexp( parts{k}, '\s+', 'split')); %split by spaces
M(k,:) = data;
end
%now assign variables
for k=1:ncol,
row = M(:,k);
eval( sprintf('%s=row', columns{k}));
end
Keep in mind that this will regard all text as cell arrays of characters. To convert to numeric arrays, you will have to do some more work-- one of the difficulties is how to distinguish between pure text (e.g. 'OK'), and numeric data with chars in between (like the comma delimited list in data_name3).
Petrus
Petrus 2012-10-18
I will try this. Thanks a lot. Question was in a more general situation, yes. Text file can be up to 400Mb and can be loaded into workspace (in fact I have about 10 files of this size but I defined a loop for each file).
My main pb was that it could take hours notably due to the use of readtext and mainly due to the eval function (ncol ~= 200; nrow ~= 1000000) when trying assigning the value (remaining part of code you mentionned). See part of code hereafter (variable 'a' being the cell output from readtext ; which gathers all data).
The treatment of numeric vectors (1000000 x 3) takes much more time (x10000) than numeric scalar treatment ( 1000000 x 1), which seems to be non optimized :)
Thanks in advance. Pierre
for k = ind_names{K} % ind_names defines the indices to be loaded for the Kth fille (by default all)
try
ind_numeric = isnumeric(cell2mat(a(2:end,k)));
catch
ind_numeric = 0;
end
if ind_numeric == 1 && isempty( min(strfind(a{2,k},',')) ) == 1
eval( [ a{1,k} '_ref = cell2mat(a(2:end,k));'] );
else
if min(strfind(a{2,k},',')) > 1
for j = 2:size(a,1)
eval( [ a{1,k} '_ref(j-1,:) = str2num(a{j,k});'] );
end
else
eval( [ a{1,k} '_ref = a(2:end,k);'] );
end
end
end

请先登录，再进行评论。

更多回答（0 个）

类别

在 Help Center 和 File Exchange 中查找有关 Environment and Settings 的更多信息

标签

产品

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by