Prompt to import data from csv file with specific column vectors

Hi everyone,

My task is to have matlab allow a user to open a file with the ability to later use these column vectors in a plot on an interval. I've dabbled into using csvread, but I can't seem to get it to work properly, so thats why I've shifted gears to look into the import data tool, because it works and it doesn't skew some of the data points like other commands. However, to pass this code onto the next person, I want to make it as simple as possible where they could run the code to be prompted to pick a .csv file, wherever it may be on their computer.

The other part of my question has to do with the intervals of plotting points. These files will typically see about 11,000 rows of data. What I would like some help on, is an efficient way to change the amount of points called out. I imagine I will later implement some sort of loop to eliminate the need for the user to edit code for optimal data points.

Whatever hints, tips or tricks you have are all greatly appreciated!! Thank you!

Answer 1

[KL]

One of the things I love about MATLAB is its extensive documentation. Here's a link for you

https://www.mathworks.com/help/matlab/ref/uigetfile.html

This does exactly what you intend to do. Combine it with a data importing function. If you're using relatively newer version, I'd highly recommend using readtable to import data.

https://www.mathworks.com/help/matlab/ref/readtable.html

Hope it helps!

[Dylan Mecca]

So far, this is very helpful. However, I'm running into an issue witht ehreadtable command. It spits these errors to me: Error using table.readFromFile (line 17) The file extension '.CSV' is not recognized.

Error in readtable (line 118)

t = table.readFromFile(filename,varargin);

Error in prac8 (line 6) T = readtable(FileName)

When I change it to look for a .xlsx file, it works good, with the exception it skews my data differently then mentioned in my initial question. This leads me to think that the I'm not quite using the readtable function properly?

So far, my code is:

clear; clc;

[FileName,PathName] = uigetfile('*.csv','Select the DVSS CSV file'); T = readtable(FileName)

[KL]

A lot depend on the data you're playing with. Just attach (using the paperclip button) some sample data which replicates your situation.

[Dylan Mecca]

What kind of parameters would keep this code from working as far as the data I'm using? Is there a way I can tell matlab to ignore certain colums and the first row of data?

[KL]

Your CSV file behaves strangely. I reckon this has something to do with the encoding, probably from where you get the data. I opened it with notepad++ and saved it under a new name. Try this file (attached) and see if the read data is ok.

 data = readtable('dummy_data.csv');

Is there a way I can tell matlab to ignore certain colums and the first row of data?

Yes, you could force your code to read only a certain range or ignore few rows/columns. Functions such as csvread or dlmread aren't necessarily bad. Just test each command with your code and see which one suits your needs.

https://www.mathworks.com/help/matlab/ref/csvread.html

I always find the See also section of the doc page really interesting, so have a look there as well. Another option is using good old textscan with fopen with a format text specifying how your file should be read. This gives you the explicit control of how you want to read your data.

You could use tic/toc to analyse your code's performance.

[Dylan Mecca]

It doesn't look like the data that you've attached is working either.

I'm getting new errors:

 Error using table/readTextFile (line 98)
Unable to open file 'dummy_data.csv'.
Error in table.readFromFile (line 33)
t = table.readTextFile(filename,otherArgs);
Error in readtable (line 118)
t = table.readFromFile(filename,varargin);
Error in prac8 (line 8)
Data = readtable('dummy_data.csv')

[KL]

I tested the file before giving it to you. I could import all 10588 rows just without any problems.

Which version of MATLAB are you using? And on which OS are you running?

[Dylan Mecca]

2014a and windows 7 64bit

[KL]

Hmm.. Do you have the file in the same folder as that of your prac8.m file? Nevertheless you could use absolute path since you get the path from uigetfile.

 [FileName,PathName] = uigetfile('*.csv','Select the DVSS CSV file');
 T = readtable(fullfile(PathName,FileName))

Also keep the whole thing in a folder where you have read/write access. If this doesn't resolve your issue, try the other commands such as csvread, dlmread, textscan etc.