FormatFloat (Convert Floating Point to String)

FormatFloat converts a floating-point number (Float) into a String using a printf-style format pattern (similar to C’s printf). Use it when you need a number to appear in text output (serial messages, display strings, custom log lines, etc.). If you need to format multiple values (time + several numbers, mixed types) into one string, consider using Sprintf instead.

Syntax

String = FormatFloat ( Float, FormatString )

Example

Example1:

The following program shows the use of the FormatFloat instruction. Using the software's numeric monitor, enter a value into FloatVal that should be converted into a string value.

Public FloatVal as Float
Public StringVal as String * 20

BeginProg
Scan (1,Sec,3,0)
StringVal = FormatFloat (FloatVal,"%f")
NextScan
EndProg

Example 2:

The following program example is useful when a display expects a clean numeric string with fixed decimal places.

Public AirTemp_C
Dim OutString As String * 20
BeginProg
  Scan(1,Sec,0,0)
    SerialOpen (ComC1,-9600,0,0,50)
    ' Example measurement
    AirTemp_C = 23.4567
    ' Format to 2 decimal places
    OutString = FormatFloat("%.2f", AirTemp_C)
    ' Send to serial display with carriage return/line feed
    SerialOut(COMC1, OutString & CHR(13) & CHR(10), "", 0, 0)
  NextScan
EndProg

Example 3:

The following is an example of formatting output so it is easily read by a person.

Public BattV
Dim OutString As String * 40
BeginProg
    SerialOpen (ComC1,-9600,0,0,50)
  Scan(10,Sec,0,0)
    ' Example measurement
    BattV = 12.9876
    ' Build a labeled message
    OutString = "Battery Voltage: " & FormatFloat("%.2f", BattV) & " V"
    ' Send message
    SerialOut(ComC1, OutString & CHR(13) & CHR(10), "", 0, 0)
  NextScan
EndProg

Example 4:

This example is useful when another device or file expects comma-separated values.

Public AirTemp_C, RH, BattV
Dim OutString As String * 80
BeginProg
    SerialOpen (ComC1,-9600,0,0,50)
  Scan(10,Sec,0,0)
    'Example measurements
    AirTemp_C = 22.5
    RH = 56.234
    BattV = 12.987
    'Create CSV text line
    OutString = FormatFloat("%.1f", AirTemp_C) & "," & _
                FormatFloat("%.1f", RH) & "," & _
                FormatFloat("%.2f", BattV)
    'Send CSV line
    SerialOut(ComC1, OutString & CHR(13) & CHR(10), "", 0, 0)
  NextScan

EndProg

Remarks

The string conversion of the floating point value is formatted based on the FormatString parameter.

For a video tutorial on using FormatFloat, see: Creating Custom Data Output in CRBasic: Formatting Numbers with FormatFloat .

Parameters

Float (Floating Point)

The variable or constant that holds the floating point value to be converted.

Type: Variable or Constant

FormatString

Determines how the floating point value will be represented in the converted string.

Most formats follow this template: %[width].[precision]type

Where:

% means: “a formatted value goes here.” Everything after % up to the final type letter describes how to format width and precision.
width (optional) is the minimum number of characters to use (pads with spaces unless zero-pad is used)

TIP:
If precision is not specified the default is 6 decimal places, regardless of the width parameter.
precision (optional) = number of digits after the decimal (for f)
type = formatting style: f, e/E, or g/G

Supported Type Codes

%f — Fixed decimal notation
%e / %E — Scientific notation
%g / %G — “General” (use the shortest representation; chooses f or e)

Example formats for a floating point value
Format String	Original value	Formatted value	Format description
"%f"	22.5	22.500000	Default 6 decimals
"%.2f"	22.5	22.50	2f specifies 2 decimals. No specified total width
"%8.2f"	22.5	22.50	Total width = 8; decimals = 2. Notice 3 leading spaces
"%08.2f"	22.5	00022.50	Total width = 8; decimals = 2. Zero=padded so 0s replace spaces
"%e"	22.5	2.250000e+01	Scientific notation; Width = 8
"%g"	22.5	22.5	General; most compact

NOTE: Y and Z in the table below are only place holders. Replace the them with numbers.

Type Code	Description (m = mantissa; d = decimal; x = exponent)
%f	Decimal notation in the form of ±mmm.dddddd; precision is 6 places to the right of the decimal.
%e (or %E)	Decimal notation in the form of ±m.dddddd e±xx; precision is 6 places to the right of the decimal.
%g (or %G)	Mantissa and decimal are variable; trailing 0s and decimals are omitted if the input has a precision less than specified by the format string.
%Y.Zf	Decimal notation in the form of ±m.d; field width is defined by Y and includes the sign and decimal place. Precision is defined by Z.
%0Y.0Zf	Decimal notation in the form of ±m.d; field width is defined by Y and includes the sign and decimal place. The mantissa will be padded by leading 0s if necessary. Precision is defined by Z. The decimal will be padded with trailing 0s.
%Ye (or %YE)	Decimal notation in the form of ±m.d e±xx; field width is defined by Y and includes the sign and decimal place.
%Yg (or %YG)	Mantissa and decimal are variable; field width is defined by Y and includes the sign and decimal place.

Right-click the parameter to display a list of options. The format string must be enclosed in quotes.

Including Literal Text

Other ASCII characters may be included in the format string. The %... portion inserts the formatted number; everything else inside the quotes is literal text.

Example:

StringVal = FormatFloat(FloatVal, "Temp=%.1f C")

Returns Temp= 23.5 C