readtable failing on MATLAB documentation example

I am trying to perform a read of a simple CSV file. When my code did not work, I decided to run the exact example provided in the MATLAB documentation. I get the exact same cryptic error message. Otherwise MATLAB seems to be working perfectly.

Matlab example .csv data, I placed in "test.txt" (I also tried with "test.csv")

LastName,Gender,Age,Height,Weight,Smoker
Smith,M,38,71,176,1
Johnson,M,43,69,163,0
Williams,F,38,64,131,0
Jones,F,40,67,133,0
Brown,F,49,64,119,0

commands run after a "clear all"
filename = "test.txt"
T = readtable(filename);

resulting MATLAB error message:
Error using readtable (line 216)
  REPLACE: "what" and "by" matrices incompatible

Note: readtable detected the following parameters:
'Delimiter', ',', 'HeaderLines', 0, 'ReadVariableNames', true, 'Format', ''

I traced execution through the MATLAB's readtable.m and subsquent calls and verified that the file is opening, the header line is read, and initially the "guessed format" appears correct. After determining the data format, MATLAB raises an exception at the next higher step in the call hierarchy. I've tried quite a few variations with and without various function options/arguments.

Any idea what I am doing wrong?

[dpb]

Which release and is this new installation or upgrade? Has readtable ever worked properly with this install?

Can't reproduce symptom here--

>> filename = fullfile(matlabroot,'examples','matlab','myCsvTable.dat');
>> readtable(filename)
ans =
  5×6 table
      LastName      Gender    Age    Height    Weight    Smoker
    ____________    ______    ___    ______    ______    ______
    {'Smith'   }    {'M'}     38       71       176        1   
    {'Johnson' }    {'M'}     43       69       163        0   
    {'Williams'}    {'F'}     38       64       131        0   
    {'Jones'   }    {'F'}     40       67       133        0   
    {'Brown'   }    {'F'}     49       64       119        0   
>> 
>> ver
-----------------------------------------------------------------------------------------------------
MATLAB Version: 9.7.0.1261785 (R2019b) Update 3
...

[Steven Lord]

Let's make sure you're using the readtable function included in MATLAB. What does this command display?

which -all readtable

[Brad Fennell]

which -all readtable

C:\RTN\MATLAB\R2018b\toolbox\matlab\iofun\readtable.m

[Image Analyst]

Mine shows

>> which -all readtable

C:\Program Files\MATLAB\R2020b\toolbox\matlab\iofun\readtable.m

C:\Program Files\MATLAB\R2020b\toolbox\shared\io\general\+matlab\+io\@ImportOptions\ImportOptions.m % matlab.io.ImportOptions method

Can you upgrade to the newest version? why stay stuck on a 2 year old version?

[dpb]

That's what R2019b shows; R2017b shows the one file; I don't have R2018b installed to check.

OP could also check to see if are updates to the release he has installed.

Answer 1

[Brad Fennell]

This is a new install from over a year ago. While I have used readtable on other installations successfully, I don't think I have used it on this computer. After continuing to research I found the following useful suggestion:

opts = detectImportOptions(tempdata);
t = readtable(tempdata, opts);

I just confirmed this suggestion worked both for the example and for my real data. I suggest that the current readtable has a bug (in my installation). When I was tracing it appeared the execution path resulted in the inability of the lower level function to populate the opts structure with auto detected data. I assume the workaround above successfully populates the opts structure in advance allowing the function to work properly. I don't know what is different about this installation versus those that work properly. The following is call hierarchy.

readtable.m

table.readFromFile...

table.readTextFile...

guessFormat

matlab.io.internal.text.determineFormatString(...

function val = get.VariableTypes(obj)

val = {obj.var_opts.Type};

val contains what looks like valid types with correct dimensions, however, if you try to examine

obj.var_opts.Type

the following error is raised

An unexpected error has occurred:

In class 'matlab.io.ImportOptions', the get method for Dependent property 'VariableTypes' attempts to access the stored property value. Dependent properties don't store a value and can't be accessed from their get method.

As soon as you step out, guessFormat raises an exception in the try/catch.

The good news is the suggestion to use detectImportOptions is an acceptable workaround so I am progressing once again :-)

[dpb]

As Steven L, suggests, show us what

which -all readtable

shows and we still don't know which release you're running, either.

Answer 2

[Brad Fennell]

which -all readtable

C:\RTN\MATLAB\R2018b\toolbox\matlab\iofun\readtable.m

Answer 3

[Brad Fennell]

Hmm, when I posted the question it asked for the release and I thought it would be visible. Sorry. Here it is

-----------------------------------------------------------------------------------------------------

MATLAB Version: 9.5.0.944444 (R2018b)

MATLAB License Number: ******

Operating System: Microsoft Windows 10 Enterprise Version 10.0 (Build 17763)

Java Version: Java 1.8.0_152-b16 with Oracle Corporation Java HotSpot(TM) 64-Bit Server VM mixed mode

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