Find a specific value in a csv file

file_name = 'table_data.csv';
C = readcell(file_name,'Delimiter',',','NumHeaderLines',1);
years = regexp(C(:,1),'(\d{4})','tokens','once');
years = vertcat(years{:})
years = 5×1 cell array
    {'2022'}
    {'2021'}
    {'2020'}
    {'2019'}
    {'2018'}
d = regexp(C(:,end),'D:"(\d+)"','tokens','once');
d = vertcat(d{:})
d = 5×1 cell array
    {'1'}
    {'2'}
    {'3'}
    {'4'}
    {'5'}
% result as a cell array of character vectors:
result = [years d]
result = 5×2 cell array
    {'2022'}    {'1'}
    {'2021'}    {'2'}
    {'2020'}    {'3'}
    {'2019'}    {'4'}
    {'2018'}    {'5'}
% result as a numeric matrix:
result = str2double([years d])
result = 5×2
        2022           1
        2021           2
        2020           3
        2019           4
        2018           5

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Voss 2022-7-16

在 MATLAB Online 中打开

table_data.csv

file_name = 'table_data.csv';
C = readcell(file_name,'Delimiter','\t','NumHeaderLines',1)
C = 5×2 cell array
    {'A/1/2/AB0000/2022abc'}    {'"B":"1", "C":"2", "D":"1"'}
    {'A/1/2/AB0000/2021abc'}    {'"B":"1", "C":"2", "D":"2"'}
    {'A/1/2/AB0000/2020abc'}    {'"B":"1", "C":"2", "D":"3"'}
    {'A/1/2/AB0000/2019abc'}    {'"B":"1", "C":"2", "D":"4"'}
    {'A/1/2/AB0000/2018abc'}    {'"B":"1", "C":"2", "D":"5"'}
years = regexp(C(:,1),'/(\d{4})','tokens','once');
years = vertcat(years{:})
years = 5×1 cell array
    {'2022'}
    {'2021'}
    {'2020'}
    {'2019'}
    {'2018'}
d = regexp(C(:,end),'"D":"(\d+)"','tokens','once');
d = vertcat(d{:})
d = 5×1 cell array
    {'1'}
    {'2'}
    {'3'}
    {'4'}
    {'5'}
% result as a cell array of character vectors:
result = [years d]
result = 5×2 cell array
    {'2022'}    {'1'}
    {'2021'}    {'2'}
    {'2020'}    {'3'}
    {'2019'}    {'4'}
    {'2018'}    {'5'}
% or, result as a numeric matrix:
result = str2double([years d])
result = 5×2
        2022           1
        2021           2
        2020           3
        2019           4
        2018           5

Voss 2022-7-16

在 MATLAB Online 中打开

table_data.csv

I'm not sure what you mean by "read next tab", because the file is read using tab as the delimiter:

file_name = 'table_data.csv';
C = readcell(file_name,'Delimiter','\t','NumHeaderLines',1)

so there are no tabs in C:

contains(C,sprintf('\t'))

However, if you want to get the part between the last slash and the end (which corresponds to where the tabs are in the file), of each character vector in the first column of C, you can do this:

% match a slash followed by any non-slash characters, occurring at the end
% (to prevent matching previous slash+stuff parts)
years = regexp(C(:,1),'/([^/]*)$','tokens','once');
years = vertcat(years{:})

And to make the regular expression for the "D" part more general (allow matching anything between the double-quotes, not just digits), you can do this:

% match the literal "D":" and return any characters after that, before the next '"'
d = regexp(C(:,2),'"D":"(.*?)"','tokens','once');
d = vertcat(d{:})

More about Regular Expressions: Operators and Characters in Regular Expressions

Voss 2022-7-17

在 MATLAB Online 中打开

table_data.csv

Another way to use regular expressions to achieve the same result would be to operate on the contents of the file directly, i.e., not on a cell array that comes from readcell.

Here's how that would work:

file_name = 'table_data.csv';
fid = fopen(file_name);
data = fread(fid,'*char').'; % read the file as a character vector
fclose(fid);
disp(data);
﻿Part 1	Part 2
A/1/2/AB0000/2022abc	"""B"":""1"", ""C"":""2"", ""D"":""1"""
A/1/2/AB0000/2021abc	"""B"":""1"", ""C"":""2"", ""D"":""2"""
A/1/2/AB0000/2020abc	"""B"":""1"", ""C"":""2"", ""D"":""3"""
A/1/2/AB0000/2019abc	"""B"":""1"", ""C"":""2"", ""D"":""4"""
A/1/2/AB0000/2018abc	"""B"":""1"", ""C"":""2"", ""D"":""5"""
% match a slash, followed by any non-slash non-tab characters, followed by
% a tab, and return the stuff between the slash and the tab
% (note: not using 'once' this time because this regexp operates on the 
% file's entire contents)
years = regexp(data,'/([^\t/]*)\t','tokens');
years = vertcat(years{:})
years = 5×1 cell array
    {'2022abc'}
    {'2021abc'}
    {'2020abc'}
    {'2019abc'}
    {'2018abc'}
% match the literal '""D"":""', return the characters after that, before the next '""'
d = regexp(data,'""D"":""(.*?)""','tokens');
d = vertcat(d{:})
d = 5×1 cell array
    {'1'}
    {'2'}
    {'3'}
    {'4'}
    {'5'}

Alexai 2022-7-19

编辑：Alexai 2022-7-19

um. sorry I have a mistake I want to read next slash ex)A/B/C0001/123456/abc0011

Thanksfully you give me a code

years = regexp(C(:,1),'/(\d{4})','tokens','once'); but I want to read next slash 123456->abc0011 How can I revise this code?

Voss 2022-7-19

在 MATLAB Online 中打开

table_data.csv

file_name = 'table_data.csv';
C = readcell(file_name,'Delimiter','\t','NumHeaderLines',1)
C = 5×2 cell array
    {'A/1/2/AB0000/2022abc'}    {'"B":"1", "C":"2", "D":"1"'}
    {'A/1/2/AB0000/2021abc'}    {'"B":"1", "C":"2", "D":"2"'}
    {'A/1/2/AB0000/2020abc'}    {'"B":"1", "C":"2", "D":"3"'}
    {'A/1/2/AB0000/2019abc'}    {'"B":"1", "C":"2", "D":"4"'}
    {'A/1/2/AB0000/2018abc'}    {'"B":"1", "C":"2", "D":"5"'}
years = regexp(C(:,1),'/([^/]*/[^/]*)$','tokens','once');
years = vertcat(years{:})
years = 5×1 cell array
    {'AB0000/2022abc'}
    {'AB0000/2021abc'}
    {'AB0000/2020abc'}
    {'AB0000/2019abc'}
    {'AB0000/2018abc'}

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Answer 2

Abderrahim. B 2022-7-15

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1761085-find-a-specific-value-in-a-csv-file#answer_1008435

在 MATLAB Online 中打开

Hi!

Try this:

% Create, split, and extract from part 1
part1  =  "A/1/2/" + string(2022:-1:2018) ;
part1 = split(part1, '/') ;
yrs = part1(:,:,end) ;
% Create, split, and extract from part 2
part2 = " ""B"":""1"", ""C"":""2"", ""D"":""" + string(1:5) + '"'  ;
part2 = split(part2, '"') ;
dig = str2double(part2(:,:,end-1)) ;
% Result
result =  transpose(yrs + "," + dig ) 
result = 5×1 string array
    "2022,1"
    "2021,2"
    "2020,3"
    "2019,4"
    "2018,5"

Use datetime if you want to convert this string array to date time array.

Please keep in mind this a way from many to solve it, you can also use regular experssion or patterns to do this.

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Find a specific value in a csv file

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Find a specific value in a csv file

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