Readtable and Readmatrix Ignore Specified Range and Produce Extra Variables

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.

Answer 1

[Dyuman Joshi]

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 

[John]

Thanks!

Answer 2

[dpb]

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...

Answer 3

[Matt J]

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