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Format number in the same format as disp

Asked by Anton Gribovskiy on 22 Sep 2019 at 2:19
Latest activity Commented on by Anton Gribovskiy on 24 Sep 2019 at 20:27
I want to format number to the string with the same format as used by disp to output numbers. So I want to write function my_format that would take number and output same string as disp. I don't need new lines, just correctly formatted number. For example
>> format
>> pi
ans =
3.1416
>> my_format(pi)
ans =
'3.1416'
>> format long
>> pi
ans =
3.141592653589793
>> my_format(pi)
ans =
'3.141592653589793'

  7 Comments

disp([0.1 0.2]) will produce the same output as fprintf('%26.15g%26.15g\n', [0.1 0.2])
Nope.
>> fprintf('%26.15g%26.15g\n', [0.1 0.2])
0.1 0.2
>> disp([0.1, 0.2])
0.1000 0.2000
>> fprintf('%#10.4g%#10.4g\n', [0.1 0.2])
0.1000 0.2000
I should have specified "under format long g as that is the format we were talking about.

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2 Answers

Answer by Walter Roberson
on 23 Sep 2019 at 6:12
 Accepted Answer

matlab.internal.display.containedDisplay(value,width)
formats value according to the current format, provided that the formatted result would be that width or less. If the formatted result would be longer, it returns the empty string ""
There is a lower-level routine matlab.internal.display.containedDisplayHelper that can also accept the format specification to use such as 'longG'; it needs its input packaged a particular way though.
As of R2019b, the internal display routines appear to be:
matlab.internal.display.commandWindowWidth
matlab.internal.display.containedDisplay
matlab.internal.display.containedDisplayHelper
matlab.internal.display.dimensionString
matlab.internal.display.format
matlab.internal.display.formatSpacing
matlab.internal.display.getCellDisplayOutput
matlab.internal.display.getContainedClassName
matlab.internal.display.getDimensionSpecifier
matlab.internal.display.getHeader
matlab.internal.display.getNewlineCharacter
matlab.internal.display.getObjectHeaderHelper
matlab.internal.display.isDesktopInUse
matlab.internal.display.isHot
matlab.internal.display.language
matlab.internal.display.numericDisplay
matlab.internal.display.numericDisplayHelper
matlab.internal.display.printWrapped
matlab.internal.display.truncateLine
matlab.internal.display.wrappedLength
Some of those have .m source in toolbox/matlab/lang/+matlab/+internal/+display but most are built-in.

  1 Comment

Thank you. containedDisplay if exactly what I was looking for.

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Answer by Bruno Luong
on 22 Sep 2019 at 18:21

>> x=logspace(1,3,10)
x =
1.0e+03 *
0.0100 0.0167 0.0278 0.0464 0.0774 0.1292 0.2154 0.3594 0.5995 1.0000
>> disp(x) % same as above
1.0e+03 *
0.0100 0.0167 0.0278 0.0464 0.0774 0.1292 0.2154 0.3594 0.5995 1.0000
>> str=evalc('disp(x)');
>> fprintf('\nx =\n\n%s', str)
x =
1.0e+03 *
0.0100 0.0167 0.0278 0.0464 0.0774 0.1292 0.2154 0.3594 0.5995 1.0000

  1 Comment

Thank you. Works like a charm wrapped in strip. I understand that eval is considered to be evil, but I think that could work as a part of private method of a class.

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