Quick question regarding CSV file reading.

Question

benjamin finsås 2021-5-3

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评论： Jeremy Hughes 2021-5-4

I have two csv files with only one colum each. I want to extract only the first number (measurement counter) and Sensor output last (V), i dont care about the water temp. The second file has less measurements (rows) than the first, so i need to chop out some measurements (rows). Preferably i want to start from a specific row, for example row 3-9 in CSVfile1 and row 4-8 in CSVfile2. Can anyone explain how i could do this, if its even possible?

I also need to plot the two tables/arrays in a same graph.

Best regards,

-Ben

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Walter Roberson 2021-5-3

Can you attach a file with a few sample lines?

benjamin finsås 2021-5-3

cycle1.csv

Of course.

I use excel to open them.

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Answer 1

Mathieu NOE 2021-5-3

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hello

my quick suggestion to the quick question

fid=fopen('cycle1.csv');
e=textscan(fid,'%s','headerlines',1);
e_splitted = split(e{1},',');
outdata = cellfun(@str2num,strrep(e_splitted, '"', ''));  % remove double quotes & convert string to num
% get my Counter and Sensor_Output data
start_row = 3;
stop_row = 9;
Counter_Output = outdata(start_row:stop_row,1);
Sensor_Output = outdata(start_row:stop_row,2);

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Mathieu NOE 2021-5-3

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hello

if you want plot to operate , the x, and y vectors must be same length

so you have to make sure that Sensor_Output2 is associated with for example Counter_Output2 that is computed with the same start and stop indexes :

Counter_Output2 = outdata(start_row2:stop_row2,1);

now the last line of your code should be :

plot(Counter_Output2,Sensor_Output2);

a even more elegant way would be to vcreate a function and pass the arguments (filename, start and stop indexes ,...) so you're keeping the main section of the code clean and compact

Full code update :

fid=fopen('cycle1.csv');
fid2=fopen('cycle2.csv');
e=textscan(fid,'%s','headerlines',1);
e2=textscan(fid2,'%s','headerlines',1);
e_splitted = split(e{1},',');
e_splitted2 = split(e2{1},',');
outdata = cellfun(@str2num,strrep(e_splitted, '"', ''));% remove double quotes & convert string to num
outdata2 = cellfun(@str2num,strrep(e_splitted2, '"', ''));
% get my Counter and Sensor_Output data
start_row = 3;
stop_row = 9;
start_row2 = 4;
stop_row2 = 8;
Counter_Output = outdata(start_row:stop_row,1);
Sensor_Output  = outdata(start_row:stop_row,2);
Counter_Output2 = outdata2(start_row2:stop_row2,1);
Sensor_Output2  = outdata2(start_row2:stop_row2,2);
plot(Counter_Output,Sensor_Output);
hold on;
plot(Counter_Output2,Sensor_Output2);
hold off;

benjamin finsås 2021-5-4

You are a legend my friend.

Thanks!

Mathieu NOE 2021-5-4

my pleasure

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Answer 2

EmirBeg 2021-5-3

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编辑：EmirBeg 2021-5-3

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Data1 = readtable('cycle1.csv');
Data2 = readtable('cycle2.csv');
t1 = table2array(Data1(:,1));
SensorOutput1 = table2array(Data1(:,2));
t2 = table2array(Data2(:,1));
SensorOutput2 = table2array(Data2(:,2));
SizeDiff = size(SensorOutput1,1)-size(SensorOutput2,1);
StartingRow = 1; %set the row that you want to start with
t1 = t1(StartingRow:size(t1,1)-SizeDiff);
SensorOutput1 = SensorOutput1(StartingRow:size(SensorOutput1,1) - SizeDiff);
plot(t1,SensorOutput1);
hold on;
plot(t2,SensorOutput2);
hold off;

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Jeremy Hughes 2021-5-4

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This is a bit cumbersome:

t1 = table2array(Data1(:,1));
SensorOutput1 = table2array(Data1(:,2));
t2 = table2array(Data2(:,1));
SensorOutput2 = table2array(Data2(:,2));

It would be easier just to use dynamic variable indexing:

t1 = Data1.(1);
SensorOutput1 = Data1.(2);
t2 = Data2.(1);
SensorOutput2 = Data2.(2);

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Answer 3

Jeremy Hughes 2021-5-4

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I'd do this:

opts = detectImportOptions('cycle1.csv','Delimiter',',','VariableNamingRule','preserve');
opts.SelectedVariableNames = opts.VariableNames(1:2);
opts.DataLines = [3 9];
T1 = readmatrix('cycle1.csv',opts);
opts.DataLines = [4 8];
T2 = readmatrix('cycle2.csv',opts);