Class EngFormatter

lib/matplotlib/ticker.py:1404–1604

Format axis values using engineering prefixes to represent powers of 1000, plus a specified unit, e.g., 10 MHz instead of 1e7.

class EngFormatter(ScalarFormatter):
    """
    Format axis values using engineering prefixes to represent powers
    of 1000, plus a specified unit, e.g., 10 MHz instead of 1e7.
    """

    # The SI engineering prefixes
    ENG_PREFIXES = {
        -30: "q",
        -27: "r",
        -24: "y",
        -21: "z",
        -18: "a",
        -15: "f",
        -12: "p",
         -9: "n",
         -6: "\N{MICRO SIGN}",
         -3: "m",
          0: "",
          3: "k",
          6: "M",
          9: "G",
         12: "T",
         15: "P",
         18: "E",
         21: "Z",
         24: "Y",
         27: "R",
         30: "Q"
    }

    def __init__(self, unit="", places=None, sep=" ", *, usetex=None,
                 useMathText=None, useOffset=False):
        r"""
        Parameters
        ----------
        unit : str, default: ""
            Unit symbol to use, suitable for use with single-letter
            representations of powers of 1000. For example, 'Hz' or 'm'.

        places : int, default: None
            Precision with which to display the number, specified in
            digits after the decimal point (there will be between one
            and three digits before the decimal point). If it is None,
            the formatting falls back to the floating point format '%g',
            which displays up to 6 *significant* digits, i.e. the equivalent
            value for *places* varies between 0 and 5 (inclusive).

        sep : str, default: " "
            Separator used between the value and the prefix/unit. For
            example, one get '3.14 mV' if ``sep`` is " " (default) and
            '3.14mV' if ``sep`` is "". Besides the default behavior, some
            other useful options may be:

            * ``sep=""`` to append directly the prefix/unit to the value;
            * ``sep="\N{THIN SPACE}"`` (``U+2009``);
            * ``sep="\N{NARROW NO-BREAK SPACE}"`` (``U+202F``);
            * ``sep="\N{NO-BREAK SPACE}"`` (``U+00A0``).