Readtable and Readmatrix Ignore Specified Range and Produce Extra Variables

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John
John 2025-6-20
评论： John 2025-6-20
Ran in:
I have this very simple code:
type 2025-03-28_02-07_10-0.csv
Meas. ID, Time/Date, WV, Index, Sort #1, Sort #2, Sort #3, , 3/28/2025 2:21:22 PM, 632.8, 1.4753 , , , , , 3/28/2025 2:22:10 PM, 632.8, 1.4754 , , , , , 3/28/2025 2:22:58 PM, 632.8, 1.4754 , , , , , 3/28/2025 2:23:46 PM, 632.8, 1.4755 , , , , , 3/28/2025 2:24:34 PM, 632.8, 1.4752 , , , , , 3/28/2025 2:26:16 PM, 632.8, 1.4757 , , , , , 3/28/2025 2:27:04 PM, 632.8, 1.4757 , , , , , 3/28/2025 2:27:52 PM, 632.8, 1.4757 , , , , , 3/28/2025 2:28:40 PM, 632.8, 1.4755 , , , , , 3/28/2025 2:29:28 PM, 632.8, 1.4756 , , , , , 3/28/2025 2:31:29 PM, 632.8, 1.4756 , , , , , 3/28/2025 2:32:17 PM, 632.8, 1.4756 , , , , , 3/28/2025 2:33:05 PM, 632.8, 1.4754 , , , , , 3/28/2025 2:33:53 PM, 632.8, 1.4756 , , , , , 3/28/2025 2:34:41 PM, 632.8, 1.4754 , , , , , 3/28/2025 2:36:08 PM, 972.3, 1.4685 , , , , , 3/28/2025 2:36:56 PM, 972.3, 1.4683 , , , , , 3/28/2025 2:37:44 PM, 972.3, 1.4687 , , , , , 3/28/2025 2:38:32 PM, 972.3, 1.4687 , , , , , 3/28/2025 2:39:20 PM, 972.3, 1.4684 , , , , , 3/28/2025 2:40:44 PM, 972.3, 1.4813 , , , , , 3/28/2025 2:41:32 PM, 972.3, 1.4683 , , , , , 3/28/2025 2:42:20 PM, 972.3, 1.4684 , , , , , 3/28/2025 2:43:07 PM, 972.3, 1.4685 , , , , , 3/28/2025 2:43:55 PM, 972.3, 1.4685 , , , , , 3/28/2025 2:45:19 PM, 972.3, 1.4679 , , , , , 3/28/2025 2:46:07 PM, 972.3, 1.4696 , , , , , 3/28/2025 2:46:55 PM, 972.3, 1.4700 , , , , , 3/28/2025 2:47:43 PM, 972.3, 1.4697 , , , , , 3/28/2025 2:48:31 PM, 972.3, 1.4697 , , , , , 3/28/2025 2:50:53 PM, 403.2, 1.4929 , , , , , 3/28/2025 2:51:41 PM, 403.2, 1.4925 , , , , , 3/28/2025 2:52:29 PM, 403.2, 1.4926 , , , , , 3/28/2025 2:53:17 PM, 403.2, 1.4928 , , , , , 3/28/2025 2:54:05 PM, 403.2, 1.4925 , , , , , 3/28/2025 2:55:26 PM, 403.2, 1.4922 , , , , , 3/28/2025 2:56:14 PM, 403.2, 1.4923 , , , , , 3/28/2025 2:57:02 PM, 403.2, 1.4923 , , , , , 3/28/2025 2:57:50 PM, 403.2, 1.4926 , , , , , 3/28/2025 2:58:38 PM, 403.2, 1.4925 , , , , , 3/28/2025 3:00:32 PM, 403.2, 1.4928 , , , , , 3/28/2025 3:01:20 PM, 403.2, 1.4926 , , , , , 3/28/2025 3:02:07 PM, 403.2, 1.4928 , , , , , 3/28/2025 3:02:55 PM, 403.2, 1.4927 , , , , , 3/28/2025 3:03:43 PM, 403.2, 1.4924 , , , , Mean, , , 1.4792 , Std Dev, , , .0100 , % Std Dev, , , 0.68, Count, , , 45, Min, , , 1.4679 , Max, , , 1.4929 ,
in1 = readtable('2025-03-28_02-07_10-0.csv', 'ReadVariableNames', false, 'Range', 'C2:C3')
in1 = 2×5 table
Var1 ExtraVar1 ExtraVar2 ExtraVar3 Var5 _____ _________ _________ _________ _____ 632.8 {' '} {' '} {' '} {' '} 632.8 {' '} {' '} {' '} {' '}
in2 = readtable('2025-03-28_02-07_10-0.csv', 'ReadVariableNames', false, 'Range', 'C2:D3')
in2 = 2×6 table
Var1 Var2 ExtraVar1 ExtraVar2 Var5 Var6 _____ ______ _________ _________ _____ _____ 632.8 1.4753 {' '} {' '} {' '} {' '} 632.8 1.4754 {' '} {' '} {' '} {' '}
stupid_matlab = readtable('PATH', 'ReadVariableNames', false, 'Range', strcat('C2:D', string(ri_length)));
Unrecognized function or variable 'ri_length'.
However, it completely ignores the column portion of the range I give it. Changing the number part of the specified range changes the number of rows, but it always produces four extra columns. If I specify C2:C3, I get five columns. If I specify C2:D3, I get six columns. I have not idea where it is getting the extra columns from. I have also tried "readmatrix" and it does the exact same thing. I've attatched the .csv, but I've opened it directly and in excel and don't see anything wrong.

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采纳的回答

Dyuman Joshi
Dyuman Joshi 2025-6-20
Ran in:
From what I have understood of your query, you need to specify that you don't require Extra columns -
readtable adds variable by default (See here for documentation entry for the same)
in = readtable('2025-03-28_02-07_10-0.csv', 'ReadVariableNames', false)
in = 51×8 table
Var1 Var2 Var3 Var4 Var5 Var6 Var7 Var8 __________ ______________________ _____ ______ ____ ____ ____ _____ {0×0 char} 03/28/2025 02:21:22 PM 632.8 1.4753 NaN NaN NaN {' '} {0×0 char} 03/28/2025 02:22:10 PM 632.8 1.4754 NaN NaN NaN {' '} {0×0 char} 03/28/2025 02:22:58 PM 632.8 1.4754 NaN NaN NaN {' '} {0×0 char} 03/28/2025 02:23:46 PM 632.8 1.4755 NaN NaN NaN {' '} {0×0 char} 03/28/2025 02:24:34 PM 632.8 1.4752 NaN NaN NaN {' '} {0×0 char} 03/28/2025 02:26:16 PM 632.8 1.4757 NaN NaN NaN {' '} {0×0 char} 03/28/2025 02:27:04 PM 632.8 1.4757 NaN NaN NaN {' '} {0×0 char} 03/28/2025 02:27:52 PM 632.8 1.4757 NaN NaN NaN {' '} {0×0 char} 03/28/2025 02:28:40 PM 632.8 1.4755 NaN NaN NaN {' '} {0×0 char} 03/28/2025 02:29:28 PM 632.8 1.4756 NaN NaN NaN {' '} {0×0 char} 03/28/2025 02:31:29 PM 632.8 1.4756 NaN NaN NaN {' '} {0×0 char} 03/28/2025 02:32:17 PM 632.8 1.4756 NaN NaN NaN {' '} {0×0 char} 03/28/2025 02:33:05 PM 632.8 1.4754 NaN NaN NaN {' '} {0×0 char} 03/28/2025 02:33:53 PM 632.8 1.4756 NaN NaN NaN {' '} {0×0 char} 03/28/2025 02:34:41 PM 632.8 1.4754 NaN NaN NaN {' '} {0×0 char} 03/28/2025 02:36:08 PM 972.3 1.4685 NaN NaN NaN {' '}
%Specifying a range
in = readtable('2025-03-28_02-07_10-0.csv', 'ReadVariableNames', false, 'Range', 'B1:H5')
in = 4×7 table
Var1 Var2 Var3 Var4 Var5 Var6 ExtraVar1 ______________________ _____ ______ ____ ____ ____ _________ 03/28/2025 02:21:22 PM 632.8 1.4753 NaN NaN NaN {' '} 03/28/2025 02:22:10 PM 632.8 1.4754 NaN NaN NaN {' '} 03/28/2025 02:22:58 PM 632.8 1.4754 NaN NaN NaN {' '} 03/28/2025 02:23:46 PM 632.8 1.4755 NaN NaN NaN {' '}
%Specifying a range with no extra variable creation
in = readtable('2025-03-28_02-07_10-0.csv', 'ReadVariableNames', false, 'Range', 'B1:H5', ...
'ExtraColumnsRule', 'ignore')
in = 4×6 table
Var1 Var2 Var3 Var4 Var5 Var6 ______________________ _____ ______ ____ ____ ____ 03/28/2025 02:21:22 PM 632.8 1.4753 NaN NaN NaN 03/28/2025 02:22:10 PM 632.8 1.4754 NaN NaN NaN 03/28/2025 02:22:58 PM 632.8 1.4754 NaN NaN NaN 03/28/2025 02:23:46 PM 632.8 1.4755 NaN NaN NaN

更多回答（2 个）

dpb
dpb 2025-6-20
Ran in:
d=dir('*.csv');
opt=detectImportOptions(d.name);
tin=readtable(d.name,'Range','C2:C3','ExtraColumnsRule','ignore')
tin = 2×1 table
Var1 _____ 632.8 632.8
I don't know if Mathworks would classify the behavior as a bug or not, but is unexpected, granted. Probably worth submitting a report as a quality of implementation issue. It's complicated, so not terribly surprising there are still some warts hanging about.
You can give it a little extra help as above to avoid the issue...
Matt J
Matt J 2025-6-20
编辑：Matt J 2025-6-20
Ran in:
When I save as .xlsx, it seems to work okay,
in1 = readtable('2025-03-28_02-07_10-0.xlsx', 'ReadVariableNames', false, 'Range', 'C2:C3')
in1 = 2×1 table
Var1 _____ 632.8 632.8

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