Reading specific from user selected csv file

Hello,

I am not good at this so bear with me. I have a .csv file where I want data from column 21 from rows 2 to 633. I want the code to prompt the user to select the csv file they want to analyze. I am importing the data with:

[fname, pname] = uigetfile('*.csv');  
filename = fullfile(pname, fname);

However, because my csv file contains text I can not use csvread. Because of this I've tried textscan but am unable to extrat the specifc column and rows above.

Can someone help me write how to get the values I want and assign it to the variable "F"?

I hope I gave enough info, thanks in advance!

Answer 1

[Walter Roberson]

colwanted = 21;
wanted_first_row = 2;
wanted_last_row = 633;
format_of_wanted_information = '%f';  %change to %s if appropriate

fmt = [repmat('%s,', 1, colwanted-1), format_of_wanted_information, '%*[^\n]'];  %ignore any further columns on line

[fid, msg] = fopen(filename);
if fid < 1
    error('Failed to open file "%s' because: "%s"', filename, msg);
end

header_rows_to_skip = wanted_first_row - 1;
wanted_row_count = wanted_last_row - wanted_first_row + 1;
datacell = textscan(fid, fmt, wanted_row_count, 'Headerlines', header_rows_to_skip);
fclose(fid);

F = datacell{1};

[Anthony Urciuoli]

This is very confusing to me. Additionally, this portion:

if fid < 1
    error('Failed to open file "%s' because: "%s"', filename, msg);
end

Returns :

File: MT.m Line: 14 Column: 37

Invalid expression. Check for missing multiplication operator, missing or unbalanced delimiters, or other syntax error. To construct matrices, use brackets instead of parentheses.

I can % that portion and it will run smoothly. However, now I am trying to plot 2 colums with plot(F,G) and I receive "Not enough input arguments". Heres the code if it helps:

clc
clear
[fname, pname] = uigetfile('*.csv');  
filename = fullfile(pname, fname);
assert(exist(filename,'file')==2, '%s does not exist.', filename);

colwanted = 21;
wanted_first_row = 2;
wanted_last_row = 633;
format_of_wanted_information = '%f';  %change to %s if appropriate
fmt = [repmat('%s,', 1, colwanted-1), format_of_wanted_information, '%*[^\n]'];  %ignore any further columns on line
[fid, msg] = fopen(filename);
% % if fid < 1
% %     error('Failed to open file "%s' because "%s"', filename,) msg;
% % end
header_rows_to_skip = wanted_first_row - 1;
wanted_row_count = wanted_last_row - wanted_first_row + 1;
datacell = textscan(fid, fmt, wanted_row_count, 'Headerlines', header_rows_to_skip);
fclose(fid);
F = datacell{1};


colwanted = 18;
wanted_first_row = 2;
wanted_last_row = 633;
format_of_wanted_information = '%f';  %change to %s if appropriate
fmt = [repmat('%s,', 1, colwanted-1), format_of_wanted_information, '%*[^\n]'];  %ignore any further columns on line
[fid, msg] = fopen(filename);
% % if fid < 1
% %     error('Failed to open file "%s' because "%s"', filename,) msg;
% % end
header_rows_to_skip = wanted_first_row - 1;
wanted_row_count = wanted_last_row - wanted_first_row + 1;
datacell = textscan(fid, fmt, wanted_row_count, 'Headerlines', header_rows_to_skip);
fclose(fid);
G = datacell{1};

plot (F,G);

Thank you for your help!

[Walter Roberson]

    error('Failed to open file "%s" because: "%s"', filename, msg);

[Walter Roberson]

[fname, pname] = uigetfile('*.csv');  
filename = fullfile(pname, fname);
assert(exist(filename,'file')==2, '%s does not exist.', filename);

colswanted = [18, 21];
wanted_first_row = 2;
wanted_last_row = 633;
format_of_wanted_information = '%f';  %change to %s if appropriate

lastwanted = max(colswanted);
fmt = [repmat({'%*s,'}, 1, lastwanted), {'%*[^\n]}'];
fmt(colswanted) = {format_of_wanted_information};
fmt = strjoin(fmt, '');

[fid, msg] = fopen(filename);
if fid < 1
    error('Failed to open file "%s" because "%s"', filename, msg);
end

header_rows_to_skip = wanted_first_row - 1;
wanted_row_count = wanted_last_row - wanted_first_row + 1;
datacell = textscan(fid, fmt, wanted_row_count, 'Headerlines', header_rows_to_skip);
fclose(fid);

F = datacell{2};  %21
G = datacell{1};  %18

plot(F, G);

The message about input arguments was probably caused by my accidentally using %s instead of %*s