Can you use the whos command to identify classes

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As the title says, I'm wondering if the whos command (or an equivilent) could be used to get the range and storage requirements on a class in Matlab. For example, the 'double' class ranges from -10^308 to 10^308 amd needs 8 bytes of storage. How would I get these specs for, say, int8? Lookng on the wiki https://www.mathworks.com/help/matlab/matlab_prog/fundamental-matlab-classes.html does not give this information, so can it be obtained with a script? Thanks

Accepted Answer

Walter Roberson
Walter Roberson on 5 Oct 2022
numeric_classes = {'int8', 'uint8', 'int16', 'uint16', 'int32', 'uint32', 'int64', 'uint64', 'single', 'double'};
num_classes = length(numeric_classes);
T = table('size', [num_classes, 4], 'VariableNames', {'Class', 'bytes', 'min', 'max'}, ...
'VariableTypes', ["categorical", "double", "categorical", "categorical"]);
numeric_classes_cats = categorical(numeric_classes);
for K = 1 : num_classes
class_name = numeric_classes{K};
class_cat = numeric_classes_cats(K);
sample_variable = zeros(1, 1, class_name);
class_info = whos('sample_variable');
class_bytes = class_info.bytes;
class_bytes_str = string(class_bytes);
if isfloat(sample_variable)
class_max = realmax(class_name);
class_min = -class_max;
class_min_str = categorical(compose("%.16g", class_min));
class_max_str = categorical(compose("%.16g", class_max));
else
class_min = intmin(class_name);
class_max = intmax(class_name);
class_min_str = categorical(class_min);
class_max_str = categorical(class_max);
end
T(K, :) = {class_name, class_bytes_str, class_min_str, class_max_str};
end
T
T = 10×4 table
Class bytes min max ______ _____ _______________________ ______________________ int8 1 -128 127 uint8 1 0 255 int16 2 -32768 32767 uint16 2 0 65535 int32 4 -2147483648 2147483647 uint32 4 0 4294967295 int64 8 -9223372036854775808 9223372036854775807 uint64 8 0 18446744073709551615 single 4 -3.402823466385289e+38 3.402823466385289e+38 double 8 -1.797693134862316e+308 1.797693134862316e+308

More Answers (2)

Image Analyst
Image Analyst on 4 Oct 2022
Try this:
a=uint8([1,2,3]);
dbl = 123.456;
str = 'abc';
s = whos
s = 4×1 struct array with fields:
name size bytes class global sparse complex nesting persistent
t = struct2table(s)
t = 4×9 table
name size bytes class global sparse complex nesting persistent __________ _______ _____ __________ ______ ______ _______ __________ __________ {'a' } 1 3 3 {'uint8' } false false false 1×1 struct false {'cmdout'} 1 33 66 {'char' } false false false 1×1 struct false {'dbl' } 1 1 8 {'double'} false false false 1×1 struct false {'str' } 1 3 6 {'char' } false false false 1×1 struct false
  3 Comments
Image Analyst
Image Analyst on 5 Oct 2022
OK I see what you want now, now that I see Walter's answer which you accepted. Of course Walter has the advantage of having the Mind Reading Toolbox, which I don't have yet.
You wanted the range of built-in classes like uint8, double, etc. I thought you wanted classes like classes you made yourself with the classdef command (like my attached Excel utility class), or instances of those classes (actual variables you instantiated as being an instance of the class) or instances of built-in class variables.

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Steven Lord
Steven Lord on 5 Oct 2022
For the integer types see this documentation page.

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