Can I make readtable to be of single precision for numeric values?

Hello everybody,

I am running an extensive for-loop inside a while-loop that at each respective iteration optimizes a different problem and pass information between each optimization. Given that I want to make it faster and consume less memory, I have been trying different approaches and want the optimization process to use single-precision variables as much as possible.

However, an important chunk of variables are created when the code reads information from external files using readtable, and I want to make sure that the numeric values or numeric variables are of single precision.

Have not been able to find some information about it in the documentation. So, my question is: ¿is there a way for me to make numeric variables/numeric input of readtable to be of single precison?

Thanks everybody for their time.

Answer 1

[Stephen23]

"¿is there a way for me to make numeric variables/numeric input of readtable to be of single precison?"

Two approaches to specify the class of numeric data when importing numeric data:

1. specify the FORMAT option (using TEXTSCAN() formats)
2. use SETVARTYPE() before calling READTABLE().

Method 1: FORMAT option:

The READTABLE documentation explains the FORMAT option in the text file options section:

https://www.mathworks.com/help/matlab/ref/readtable.html#mw_47bd1f02-32a6-44af-aedd-70395ba4c587

The format that used by TEXTSCAN():

https://www.mathworks.com/help/matlab/ref/textscan.html#btghhyz-1-formatSpec

fnm = 'test.txt';
tb1 = readtable(fnm, 'Format','%f32%f%f') % first column SINGLE

tb1 = 4×3 table
    X     Y     Z 
    __    __    __

    11    12    13
    21    22    23
    31    32    33
    41    42    43

class(tb1.X)

ans = 'single'

Method 2: SETVARTYPE() function:

The READTABLE() documentation describes the import options object here:

https://www.mathworks.com/help/matlab/ref/readtable.html#mw_da8f54b7-5bd3-4640-9eb5-715f76a3a7f0

The supporting functions are:

https://www.mathworks.com/help/matlab/ref/detectimportoptions.html

https://www.mathworks.com/help/matlab/ref/matlab.io.text.delimitedtextimportoptions.setvartype.html

obj = detectImportOptions(fnm);
obj = setvartype(obj,'X','single'); % first column SINGLE
tb2 = readtable(fnm, obj)

tb2 = 4×3 table
    X     Y     Z 
    __    __    __

    11    12    13
    21    22    23
    31    32    33
    41    42    43

class(tb2.X)

ans = 'single'

[Kenny Giron]

Thank you. Now I understand how to browse deeper in the documentation. I need to dig deeper in the supporting functions and the additional links shown in the main function documentation.

I think the SetVarType is so much more intuitive though. Thanks for showing me that.