Using string() on double values without automatic rounding?

Hello,

When i use string() with double values, the number is converted to a string where the number is rounded to four decimals, even when there are more decimals in the original double value. Image:

I am currently writing a conversion script where i need the extra decimals. Is it possible to disable this automatic rounding?

Thank you.

Answer 1

[Matt J]

even when there are more decimals in the original double value

There are no more decimals in the original double value. A double value can only have 15 digits of precision.

[Sondre]

I'm not sure im following? If I understand correctly, a double value can have 15 decimal places of precision. Even with numbers with less than 15 digits in total the problem is still there:

Meaning that the string() function rounds to four decimals. My question is wether it is possible to do this double->string conversion without this rounding.

I hope i have made myself more clear, sorry if my initial formulation was off.

[Matt J]

You could use num2str,

string( num2str(123.123123123,'%.9f') )

ans = "123.123123123"

[Sondre]

Thanks!

Answer 2

[Stephen23]

Rather than slow NUM2STR and then STRING, for a scalar the simpler and more efficient approach is to just call SPRINTF:

sprintf("%.9f",123.123123123)

ans = "123.123123123"

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

For non-scalar values use COMPOSE:

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