removevars ERROR for a table

Hello gusy!

I am starting with new project for my wokr I I got stuck in the beggining.

I am making simple coda in app designer to load a CVS, delete some rows i dont need and then plot a resuts.

Having

Error using tabular/subsasgnParens (line 215)

A table variable subscript must be a numeric array containing real positive integers, a logical array, a character vector, a string array, or a cell array of character vectors.

Error in tabular/removevars (line 28)

a = move(a).subsasgnParens({':',vars},[],false,true);

[file,path,~] = uigetfile({'.csv'}); % open the dialog box, 
           
                % N = file; %create variable with the name of the document
                 %app.EditField.Value = N; % show document name in text filed
         
filename = [path file]; %combine path and name 

A1= readtimetable(filename); %importing data to parameter AA as a table
                %A1.Properties.VariableDescriptions % original names for variables from the logs, before MATLab changed them.
         
                
 A2 = removevars(A1,{'Lon' 'Lat' 'GPSAltitude_m_' 'GPSTime' 'GPSHead' 'GPSSource' 'GPSDataInd' 'GPSArea' 'LTEKPIPCellServingEARFCN_DL_' ...
  'LTEKPIPCellServingEARFCN_UL_' 'LTEKPIPCellServingBandWidthDL' 'LTEKPIPCellServingBandWidthUL' 'LTEKPIPCellPUSCHPowerdBm' 'LTEKPIPCellPUCCHPowerdBm' ...
   'LTEKPIPCellSRSPowerdBm' 'LTEKPIPCellTotalTxPowerdBm' 'LTEKPIPCellWBCQICW0' 'LTEKPIPCellWBRI' 'LTEKPIPCellWBRI1Rate' 'LTEKPIPCellWBRI2Rate' ...
   'LTEKPIPCellWBRI3Rate' 'LTEKPIPCellWBRI4Rate' 'LTEKPIPCellDLMCS0' 'LTEKPIPCellDLMCS1' 'LTEKPIPCellULMCS' 'LTEKPIPCellDLModulation0' ...
   'LTEKPIPCellDLModulation1' 'LTEKPIPCellULModulation' 'LTEKPIPCellPDSCHPRBNumberTB0Including0' 'LTEKPIPCellPDSCHPRBNumberTB1Including0' ...
    'LTEKPIPCellPUSCHPRBNumberIncluding0' 'LTEKPIPCellPDSCHBLER' 'LTEKPIPCellPUSCHBLER' 'LTEKPIPCellPUSCHThroughputMbps' 'LTEKPIPCellMACDLThroughputMbps' ...
    'LTEKPIPCellMACULThroughputMbps' 'LTEKPIPDSCHPRBNumberAvgTotal' 'LTEKPIPUSCHPRBNumberAvgTotal' 'LTEKPIPDSCHPRBNumberIncluding0Total' ...
    'LTEKPIPUSCHPRBNumberIncluding0Total' 'LTEKPIPDSCHBLER' 'LTEKPIPUSCHBLER' 'LTEKPIPDSCHThroughputMbps' 'LTEKPIPUSCHThroughputMbps' ...
     'LTEKPIMACDLThroughputMbps' 'LTEKPIMACULThroughputMbps' 'LTEKPIRLCDLThroughputMbps' 'LTEKPIRLCULThroughputMbps' 'LTEKPIPDCPDLThroughputMbps' ...
      'LTEKPIPDCPULThroughputMbps' 'LTEKPITAC' 'LTEKPICAType' 'LTEKPIULCAType' 'LTEKPIBandCombination' ...
     'QualcommLteLteAdvIntrafreqMeasurePCellNeighborCellNeighborCellC' 'QualcommLteLteAdvIntrafreqMeasurePCellNeighborCellNeighborCellL' ...
    'QualcommLteLteAdvIntrafreqMeasurePCellNeighborCellSummaryNeighb' 'QualcommLteLteAdvIntrafreqMeasurePCellNeighborCellNeighborMeasu'});
             % delete all shitty collums I dont need
        
        

this is the CSV I am working with.

https://drive.google.com/drive/folders/1nCXV5Stf-5oMKg3asAsr2PF0YbLflIs3?usp=sharing

Please be kind and explaing stuff because I might be dumb :D

thanks

Answer 1

[Karel Starý]

Yeah, it seems like it does not rekognize the name BUT I am positive, its there. Original name for the row is LTEKPIPCellServingBandWidthUL but ater I load the file via readtimetable it change the name to LTEKPIPCellServingEARFCN_DL_. I have try all the possibilities with and withou the "_" , but still no luck (I am using R2021a which should allow the variable name with the spaces, but its not :D ) . I have tryed the approach with patients2 = patients(:, {'LastName', 'Age'}); and there I am stuck with the same issue.

SO MY ISSUE IS THAT MATLAB DOESNT RECOGNIZE MY VARIABLE NAMES CORRECTLY WHEN THERE IS A SPACE IN THE ORIGINAL NAME.

Then I watched some more vids about this and I found out that when i generate a function through the Import Data tool, it looks like this.

SO... If the original name does not contain any "wrong" character (space etc.), it will leave the variable name the same. But if there is a space or something, IT WILL RENAME THE VARIABLE "VarX" where X is the position of variable.

What a beatifull design and no documentation on this under any topic regarding readtable or etc.

Hope this will help someone some day and thanks to both of you guys whom tried to help me.

[Cris LaPierre]

What version of MATLAB are you using? Can you share your csv file? You can attach it usingn the paperclip icon. As I explain before, MATLAB may change the names to be valid variable names, but I'm surprised its changing LTEKPIPCellServingBandWidthUL to LTEKPIPCellServingEARFCN_DL_.

Table names must be valid variable names, and therefore must follow the same naming conventions as variables. When they do not, MATLAB will automatically modify them so that they do. When it does that, it provides a warning message. In R2021a, it says"

Warning: Column headers from the file were modified to make them valid MATLAB identifiers before creating variable names for the table. The original column headers are saved in the VariableDescriptions property.

Set 'VariableNamingRule' to 'preserve' to use the original column headers as table variable names.

Note that there is a 'preserve' option. This was first introduced in R2019b as 'PreserveVariableNames'. In R2020b, this was changes to 'VariableNamingRule'.

When I create a csv file using the variable names you provided, and load it using readtimetable in R2021a, it is able to do so without changing any names.

data=readtimetable('Karelnames.csv');
data.LTEKPIPCellServingBandWidthUL

ans = 9×1

0.8700 0.5309 0.0670 0.8088 0.2738 0.4512 0.1452 0.3727 0.2886

[Steven Lord]

Up through release R2019a the variable names in table and timetable arrays were required to be valid MATLAB identifiers using the rules given in the documentation for isvarname (starts with a letter, no more than namelengthmax characters, contains only numbers / letters / underscore, and is not a keyword.) In release R2019b that limitation was removed.

In previous releases, reading the data using readtable should have issued a warning that your variable names had been modified to be valid MATLAB identifiers.

[Karel Starý]

Using R2021A so it should be ok with any string (but its not). Warning is still there but from the table shown in command win. one would say it should just replace spaces with _. But in the end it replace whole name of the variable with VarX as mentioned... I am still a noob, so in the end I believe the problem is sitting on my chair anyway :D. Thanks for all the help guys ...

Answer 2

[Cris LaPierre]

I can't reproduce your error message, but I do get a different error. One of the variable names you are trying to remove does not exist in the file.

Error using tabular/subsasgnParens (line 215)

Unrecognized table variable name 'LTEKPIPCellServingBandWidthDL'.

Error in tabular/removevars (line 28)

a = move(a).subsasgnParens({':',vars},[],false,true);

Answer 3

[Steven Lord]

How many variables does your timetable have and how many do you want to keep? If you only want to keep one or two, rather than removing a lot of variables you could just index and keep the ones you want. For a sample table:

load patients
patients = table(LastName,Gender,Age,Height,Weight,Smoker,Systolic,Diastolic);

I could remove all the variables except LastName and Age:

patients1 = removevars(patients, {'Gender', 'Height', 'Weight', 'Smoker', 'Systolic', 'Diastolic'});

Or I could keep LastName and Age:

patients2 = patients(:, {'LastName', 'Age'});

Let's check that we received the same results.

areTheyTheSame = isequal(patients1, patients2)

areTheyTheSame = logical
   1

We did.