How to grab and process values from a .csv file using fgetl and sscanf?

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Preyanka Dey 2020-3-8

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/509650-how-to-grab-and-process-values-from-a-csv-file-using-fgetl-and-sscanf

评论： Preyanka Dey 2020-3-8

采纳的回答： Walter Roberson

assignment6.csv

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Can anyone please help me:

The attached assignment6.csv file contain 3 columns. I want to read, process and store the values line by line inside 4 vectors. Values from first and third column will remain as it is. However, after reading a number from second column I want pass it through a loop, and then store it into two vectors. When, I applied 'fgetl' it returns first line 2008, 1, 0. However, I can't grab the values after comma. The output should be like the following:

[y m d p] =

2008 1 1 0 % first line

2008 1 2 2 %2nd line

2008 1 3 0 %3rd line

...............................

2008 2 26 17 %2nd last line

2008 2 27 0 %last line

function [y, m, d, p] = convert_date()
fid = fopen('assignment6.csv', 'r');
y = [];
d = [];
m = [];
p = [];
for i = 1:58
tline = fgetl(fid);
out = sscanf(tline, '%d %d %d');
y1 = out(1);
d1 = out(2);
p1 = out(3);
if (fix(d1/30)==0)
    m1 = 1
    d = d1
elseif (fix(d1/30)== 1)
    m1 = fix(d1/30) + 1
    d = (d1 - 31)
end
y = [y; y1];
m = [m; m1];
d = [d; d1];
p = [p; p1];
disp ([y m d p])
end
end

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Answer 1

Walter Roberson 2020-3-8

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https://ww2.mathworks.cn/matlabcentral/answers/509650-how-to-grab-and-process-values-from-a-csv-file-using-fgetl-and-sscanf#answer_419068

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out = sscanf(tline, '%d %d %d');

Your input lines have commas in them. You should put the commas into the format:

out = sscanf(tline, '%d,%d,%d');

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Walter Roberson 2020-3-8

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It works for me when I test. However a few lines later you have a bug

if (fix(d1/30)==0)
    m1 = 1
    d = d1
elseif (fix(d1/30)== 1)
    m1 = fix(d1/30) + 1
    d = (d1 - 31)
end

The problem with that is that d is your variable that is accumulating all of the day-of-the-month information, and you are overwriting it with a scalar.

Preyanka Dey 2020-3-8

Thanks Walter Roberson for your time and patience. You are right. It is taking and processing values after comma, but not returning those in the matrix. Actually, I don't know much about syntax in Matlab. That's why I often face problems when I try to write code. Can you please suggest me any good books of Matlab? My focus is to deal with big data analysis using Matlab. Thank you.

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