MATLAB not indexing table with correct data type, how to specify da... (2024)

T = 2x1 table

ID ___ 92 NaN

T = 2x1 table

ID ____ "92" "2A"

What is the significance/purpose of using the "detectImportOptions" function? what does opts be equal to after that line is run?

Is there any way I can blanket apply that to a whole table, or would I need to set every column individually?

"What is the significance/purpose of using the "detectImportOptions" function? what does opts be equal to after that line is run?"

detectImportOptions returns a structure containing information about the default way readtable will read and interpret the file.

"Is there any way I can blanket apply that to a whole table, or would I need to set every column individually?"

See the setvartype line below for how you can apply a type to all variables in the whole table at once.

That is very cool. I will have to see about doing that. This will be awesome. This adds a lot of certainty to the code, with all the columns of data. I will try it later and mark this as an answer when it works (which I believe it really will anyways).

Thank you a lot!

You're welcome!

Wait, how would I change multiple rows to differnent data types? I do not think I can do something like this:

could I define arrays or something like that?

Also, I used the command:

I got the output:

It seems to be missing variable import properties. I do not know if that would affect anything.

"how would I change multiple rows to differnent data types?"

Do you mean multiple columns (aka table variables)?

If so, you can do them one at a time like that, or you can do them all at once:

"Also ... It seems to be missing variable import properties. I do not know if that would affect anything."

Seems like it's not detecting any variables/columns. Upload the file using the paperclip button and I can take a look.

Wait, how would I change multiple rows to differnent data types?

A variable (represented as a column) in a table array can only contain data of one type. You can't "mix and match" inside the same table variable.

Each variable in a table array can be a different type from the other variables.

So the following is a valid table, with the LastName variable being a string array, Height and Weight being double, and Smoker being logical.

If you wanted to flip this around to make a table with one variable per patient, you would not be able to do so and keep the first row of that new table a string array, the second and third rows double, and the fourth row logical. If you tried with a function like rows2vars, in this case it is technically able to make it work because MATLAB can convert doubles and logicals into a string and so turn each variable into a string array. But if T had contained another variable that wasn't able to be converted into a string, it wouldn't have worked.

So if I need to set multiple columns to multiple different data types, I cannot do those in the same line, but I can do one line per data type, like below:

Also, concerning the file, I think it is because I need the properties of a specific sheet. The excel file has multiple sheets in it. So, it seems when I do "detectImportOptions" and maybe "setvartype" I need to specify filepath and the sheet. Do you know the proper format for this?

MATLAB specifies the detectImportOptions function to follow the format:

opts = detectImportOptions(filename)

or

opts = detectImportOptions(filename,name,value)

MATLAB specifies the readtable function to follow the format:

T = readtable(filename,name,value)

or

T = readtable(filename,opts,name,value)

My MATLAB code that works to open the specific sheet properly is:

So, I believe I should maybe use:

Sorry, but I cannot share the file, it has some important info to me. Thank you for the help so far!

Hey, I'm sorry about that. I misspoke. I meant multiple columns as different data types. I did read what you said, and it is interesting. I did have a little trouble following though. I am new to MATLAB.

So, I was able to get it to work. I had to use:

I had to get rid of the 'TextType', 'string' option. It said invalid parameter or something of the like, but if I can force the data type now, then I do not need to worry about that.

This works great!! Thank you all who were involved!!

",,,I cannot do those in the same line, but I can do one line per data type"

Yes, per setvartype documentation, the type argument must be a scalar. A seemingly useful enhancement would be to let both selection and type be cellstr or string arrays with a 1:1 correspondence.

There's also a feature vartype with a table that allows you to index by the current type and convertvars will let you then change by that indexing method. Keep poking at the doc and don't stop reading at the first line; study it in depth; there's a lot hidden in the bowels a cursory glance won't tell you.

opt =

DelimitedTextImportOptions with properties: Format Properties: Delimiter: {','} Whitespace: '\b\t ' LineEnding: {'\n' '\r' '\r\n'} CommentStyle: {} ConsecutiveDelimitersRule: 'split' LeadingDelimitersRule: 'keep' TrailingDelimitersRule: 'ignore' EmptyLineRule: 'skip' Encoding: 'UTF-8' Replacement Properties: MissingRule: 'fill' ImportErrorRule: 'fill' ExtraColumnsRule: 'addvars' Variable Import Properties: Set types by name using setvartype VariableNames: {'ID1', 'ID2'} VariableTypes: {'auto', 'int32'} SelectedVariableNames: {'ID1', 'ID2'} VariableOptions: [1-by-2 matlab.io.VariableImportOptions] Access VariableOptions sub-properties using setvaropts/getvaropts VariableNamingRule: 'modify' Location Properties: DataLines: [2 Inf] VariableNamesLine: 1 RowNamesColumn: 0 VariableUnitsLine: 0 VariableDescriptionsLine: 0 To display a preview of the table, use preview

tT = 2x2 table

ID1 ID2 ___ ___ 146 146 42 42