Considering two situations:
I have a string "F2.5" and Quantity["2.3s"]. How can the numeric value be extracted to have:
"F2.5"` -> 2.5
Quantity["2.3s"]` -> 2.3
Thanks!
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3 Answers
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StringDrop["F2.5", 1] // ToExpression
StringDrop["2.5F", -1] // ToExpression
and
List @@ Quantity["2.3s"] // First
or rather as @thils proposed, directly
Quantity["2.3s"] // First
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Internal`StringToDouble seems applicable:
Internal`StringToDouble /@ {"F2.5", "2.5F"}
{2.5, 2.5}
The evaluated form of Quantity["2.3s"] is Quantity[2.3`,"Seconds"] therefore as already commented:
Quantity["2.3s"][[1]]
2.3
System`Convert`TableDump`ParseTable provides configurable options for processing strings.
answered Jun 24, 2015 at 12:27
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$\begingroup$ Nice ! I was looking in the $ImportFormats but failed to find something useful ... $\endgroup$ Commented Jun 24, 2015 at 12:31
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$\begingroup$ Do you know in which functions this internal is used ? This works:
ImportString["2.5F", "List"]but it does not for "F2.5" ...Interpreter["Number"]["F2.5"]orInterpreter["Number"]["2.5F"]do not work either ... $\endgroup$ Commented Jun 24, 2015 at 12:45 -
$\begingroup$ @SquareOne I seem to recall coming across an explicit use of
Internal`StringToDoubleby a built-in function but I cannot recall where at the moment. If I do later I'll let you know. $\endgroup$ Commented Jun 24, 2015 at 12:53
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This may be more robust, assuming you want to see the specific letter "F":
ToExpression@StringCases[ #,
{"F" ~~ s : NumberString -> s,
s : NumberString ~~ "F" -> s}] & /@
{"F3.14", "2.718F","an embedded number F2.34 in a string"}
{{3.14}, {2.718}, {2.34}}
answered Jun 24, 2015 at 13:44
QuantityMagnitude[Quantity["2.3", "Seconds"]]$\endgroup$ToExpression? $\endgroup$List @@ Quantity["2.3s"] // First$\endgroup$