A tip for specifying precision of displayed quantities.

[mateuszbaran]

I've spent about half an hour figuring it out so I think this tip may be useful for other people :slightly_smiling_face: .

[sostock]

I think the wording here is misleading: round does not “set precision of displayed value”. The round function does not display anything by itself, it returns a rounded value. Describing this as specifying precision for display sounds like it is some equivalent to printf formatting.

I think it would be good to add a section about rounding. In that section, we could explain why it is necessary to specify the output unit (or is it obvious enough?).

Note that you can also specify a unit instead of a type as first argument. We should document this as well:

julia> round(typeof(d), d; sigdigits=3)
1.74 mm

julia> round(u"mm", d; sigdigits=3)
1.74 mm

julia> round(u"m", d; sigdigits=3)
0.00174 m

[mateuszbaran]

"set precision of displayed value" is the thing I wanted to do, so to me this is the key part that needs documenting. If you thing this should be done differently than using round, I'm open to suggestions.

[mateuszbaran]

I had a quantity that, when printed it to a string, it gave me way too many digits, more than the precision with which the quantity was determined. So it looked silly and I wanted to trim it -- and it's definitely not obvious how it should be done.