How do i reset a fileID value?
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Relatively new to MATLAB so it's probably a stupid question. But when writing my code I forgot to use the fclose function in my for loop so the value kept going up. My fid value i believe should be 34 but shows as 54 (my dataset has 34 colums). How do I sort of reset my fid value? also if anyone spots anything else wrong with the code that would be great. This is only a small portion of the code as I am just trying to get this part to work first.
close all
clear all
clc
fpath=uigetdir;
files=dir([fpath '\*.csv']);
files=char(files.name);
for n=1:size(files,1)
fid=fopen([fpath '\' files(n,:)]);
data{n}=textscan(fid, '%s %f %f %f %f %f %f %f %f %f %f %f %f %f %f %f %f %f %f %f %f %f %f %f %f %f %f %f %f %f %f %f %f %f','Delimiter',',','CollectOutput',1, 'Headerlines',1);
fclose(fid);
data{1,n}{1,1}=datenum(data{1,n}{1,1},'dd-mmm-yyyy HH:MM:SS');
end
1 Comment
Some tips on looping over filenames:
fpath = uigetdir;
files = dir(fullfile(fpath,'*.csv')); % use FULLFILE rather than text concatenation.
for n = 1:numel(files) % no need for a char array...
fnm = fullfile(fpath,files(n).name); % ... you can access the structure directly.
...
files(n).data = ... optional, if you want to store any data
end
As Image Analyst wrote in your other answer, you should not convert the filenames into a character array.
Accepted Answer
Using:
should close all of them. You can then start with fid = 3.
Also, I lost count of the number of '%f' there are. You can avoid writing all that with:
['%s' repmat('%f', 1, 33)]
And I don’t understand using datenum here:
data{1,n}{1,1}=datenum(data{1,n}{1,1},'dd-mmm-yyyy HH:MM:SS');
.
15 Comments
Whale_Shark
on 24 Nov 2022
As always, my pleasure!
I very much appreciate yoiur compliment!
I would do something like this —
str = '01-Jan-2015 02:30:00';
datetime(str, 'InputFormat','dd-MMM-yyyy HH:mm:ss') % NOTE — Format Differences
Or since there appears to be no ambiguity in the dates or times, simply —
datetime(str)
Also, if you use readtable, it should do the conversion for you automatically, as well as retain the column header data (variable names) that you can then reference.
It would help to know what version/release you’re using, since there have been changes in the last few releases.
.
Whale_Shark
on 24 Nov 2022
Star Strider
on 24 Nov 2022
I’m not certain what the problem could be. The ‘Date/Time (GMT)’ data should be automatically converted to a datetime array, since there appears to be no ambiguity, although it might require adding 'TimeZone','UTC'. It would help if you could attach one of your data files.
Whale_Shark
on 25 Nov 2022
Edited: Whale_Shark
on 25 Nov 2022
The readtable funciton imports the first column automatically as a datetime array, although it doesn’t have an associated 'TimeZone' property, so I set it to 'UTC'.
Assuming that ‘Hmax’ is the maximum wave height, I have no problems retrieving it and plotting it. (Plotting all of them reveals wave heights of 10000 meters, so I assumes that codes for missing data, since a wave height of that amplitude would be notable!)
T1 = readtable('https://www.mathworks.com/matlabcentral/answers/uploaded_files/1207193/GdS_allwaveparameters2015.csv', 'VariableNamingRule','preserve')
VN = T1.Properties.VariableNames;
DT = T1.('Date/Time (GMT)')
T1.('Date/Time (GMT)').TimeZone = 'UTC'; % Set 'TimeZone' Property
T1.('Date/Time (GMT)').TimeZone % Check
figure
plot(T1.('Date/Time (GMT)'), T1.('Hmax (m)')) % Variable Name Reference
grid
xlim([0 hours(24)]+T1{1,1})
xlabel(VN{1})
ylabel(VN{5})
title('First 24 Hours Hmax')
figure
plot(T1{:,1}, T1{:,5}) % Column Index Reference
grid
xlim([0 hours(24)]+T1{1,1})
xlabel(VN{1})
ylabel(VN{5})
title('First 24 Hours Hmax')
This would likely require the Mapping Toolbox to plot with respect to the geographic coordinates. Since I don’t have it (and so have very little experience with it other than here on Answers), I defer to you for that.
.
Whale_Shark
on 25 Nov 2022
Star Strider
on 25 Nov 2022
As always, my pleasure!
Whale_Shark
on 25 Nov 2022
Whale_Shark
on 25 Nov 2022
Edited: Whale_Shark
on 25 Nov 2022
Star Strider
on 25 Nov 2022
The first instance I see of any dot indexing is in the ‘VN’ assignment. My code uses readtable, not readmatrix. Use readtable instead and see if the error persists.
Check to see what ‘T1’ is after that assignment. It should be a table and the rest of the code should then work correctly.
(Otherwise, it is possible that the file itself was not actually read, so ‘T1’ is empty.)
Whale_Shark
on 25 Nov 2022
Edited: Whale_Shark
on 25 Nov 2022
So the readmatrix was me being an idiot and not realising that i had typed readmatrix instead of readtable. It now produces the variables with the headers VN and T1 with the data values (see imported picture below),
but produces a warning and anothe error (see imported picture below).
close all
clear all
clc
%Load in the data
fpath=uigetdir;
files=dir([fpath '\*.csv']);
files=char(files.name);
%for loop to go through the variable files, creating variables for wave
%height (Hmax [H])), max period (Tmax [T]), and geographical direction in
%degrees (Directiondeg [direction]). Using textscan function to read the
%data files.
for n=1:size(files,1)
fid=fopen([fpath '\' files(n,:)]);
data{n}=textscan(fid, ['%s' repmat('%f', 1,34)],'Delimiter',',','CollectOutput',1, 'Headerlines',1);
fclose(fid);
%readtable to set datetime array for first column in the data.
T1=readtable([fpath '\' files(n,:)]);
VN=T1.Properties.VariableNames;
DT=T1.('Date/Time (GMT)');
T1.('Date/Time (GMT)').TimeZone='UTC';
T1.('Date/Time (GMT)').TimeZone
end
Star Strider
on 25 Nov 2022
Edited: Star Strider
on 25 Nov 2022
It’s not an error, simply a Warning.
My original code solves that as well:
T1 = readtable('https://www.mathworks.com/matlabcentral/answers/uploaded_files/1207193/GdS_allwaveparameters2015.csv', 'VariableNamingRule','preserve')
→ → → → → ↑
Follow the arrows to the solution.
.
Whale_Shark
on 25 Nov 2022
Star Strider
on 25 Nov 2022
As always, my pleasure!
More Answers (1)
Image Analyst
on 25 Nov 2022
0 votes
@Victoria Snell regarding your dot indexing problem, did you not see my Answer in your duplicate question:
I show you how to fix that by creating the filename properly.
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