Merge pull request #1254 from andrewgsavage/plotting_pintpandas

Plotting pintpandas
hgrecco · Mar 3, 2021 · 3cf3a81 · 3cf3a81
2 parents 2e1185c + 0ea5b90
commit 3cf3a81
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diff --git a/docs/pint-pandas.ipynb b/docs/pint-pandas.ipynb
@@ -45,7 +45,7 @@
    "source": [
     "This example will show the simplist way to use pandas with pint and the underlying objects. It's slightly fiddly as you are not reading from a file. A more normal use case is given in Reading a csv.\n",
     "\n",
-    "First some imports (you don't need to import `pint_pandas` for this to work)"
+    "First some imports"
    ]
   },
   {
@@ -55,7 +55,8 @@
    "outputs": [],
    "source": [
     "import pandas as pd \n",
-    "import pint"
+    "import pint\n",
+    "import pint_pandas",
    ]
   },
   {
@@ -218,12 +219,13 @@
    "metadata": {},
    "outputs": [],
    "source": [
-    "test_data = '''speed,mech power,torque,rail pressure,fuel flow rate,fluid power\n",
-    "rpm,kW,N m,bar,l/min,kW\n",
-    "1000.0,,10.0,1000.0,10.0,\n",
-    "1100.0,,10.0,100000000.0,10.0,\n",
-    "1200.0,,10.0,1000.0,10.0,\n",
-    "1200.0,,10.0,1000.0,10.0,'''"
+    "test_data = '''ShaftSpeedIndex,rpm,1200,1200,1200,1600,1600,1600,2300,2300,2300\n",
+    "pump,,A,B,C,A,B,C,A,B,C\n",
+    "ShaftSpeed,rpm,1200,1200,1200,1600,1600,1600,2300,2300,2300\n",
+    "FlowRate,m^3 h^-1,8.72,9.28,9.31,11.61,12.78,13.51,18.32,17.90,19.23\n",
+    "DifferentialPressure,kPa,162.03,144.16,136.47,286.86,241.41,204.21,533.17,526.74,440.76\n",
+    "ShaftPower,kW,1.32,1.23,1.18,3.09,2.78,2.50,8.59,8.51,7.61\n",
+    "Efficiency,dimensionless,30.60,31.16,30.70,30.72,31.83,31.81,32.52,31.67,32.05'''"
    ]
   },
   {
@@ -240,7 +242,7 @@
    "metadata": {},
    "outputs": [],
    "source": [
-    "df = pd.read_csv(io.StringIO(test_data), header=[0, 1])\n",
+    "df = pd.read_csv(io.StringIO(test_data), header=[0, 1], index_col = [0,1]).T\n",
     "# df = pd.read_csv(\"/path/to/test_data.csv\", header=[0, 1])\n",
     "df"
    ]
@@ -275,7 +277,7 @@
    "cell_type": "markdown",
    "metadata": {},
    "source": [
-    "As previously, operations between DataFrame columns are unit aware"
+    "Let's confirm the units have been parsed correctly"
    ]
   },
   {
@@ -284,7 +286,14 @@
    "metadata": {},
    "outputs": [],
    "source": [
-    "df_.speed * df_.torque"
+    "df_.dtypes"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "Here the h in m^3 h^-1 has been parsed as the planck constant. Let's change the unit to hours."
    ]
   },
   {
@@ -293,7 +302,15 @@
    "metadata": {},
    "outputs": [],
    "source": [
-    "df_"
+    "df_['FlowRate'] = pint_pandas.PintArray(df_['FlowRate'].values.quantity.m, dtype = \"pint[m^3/hr]\")\n",
+    "df_.dtypes"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "As previously, operations between DataFrame columns are unit aware"
    ]
   },
   {
@@ -302,8 +319,17 @@
    "metadata": {},
    "outputs": [],
    "source": [
-    "df_['mech power'] = df_.speed * df_.torque\n",
-    "df_['fluid power'] = df_['fuel flow rate'] * df_['rail pressure']\n",
+    "df_.ShaftPower / df_.ShaftSpeed"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "df_['ShaftTorque'] = df_.ShaftPower / df_.ShaftSpeed\n",
+    "df_['FluidPower'] = df_['FlowRate'] * df_['DifferentialPressure']\n",
     "df_"
    ]
   },
@@ -336,8 +362,9 @@
    "metadata": {},
    "outputs": [],
    "source": [
-    "df_['fluid power'] = df_['fluid power'].pint.to(\"kW\")\n",
-    "df_['mech power'] = df_['mech power'].pint.to(\"kW\")\n",
+    "df_['FluidPower'] = df_['FluidPower'].pint.to(\"kW\")\n",
+    "df_['FlowRate'] = df_['FlowRate'].pint.to(\"L/s\")\n",
+    "df_['ShaftTorque'] = df_['ShaftTorque'].pint.to(\"N m\")\n",
     "df_.pint.dequantify()"
    ]
   },
@@ -374,6 +401,49 @@
     "df_.pint.to_base_units().pint.dequantify()"
    ]
   },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+   "## Plotting\n",
+    "Pint's matplotlib support allows columns with the same dimensionality to be plotted."
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "pint_pandas.PintType.ureg.setup_matplotlib()\n",
+    "ax = df_[['ShaftPower', 'FluidPower']].unstack(\"pump\").plot()"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "ax.yaxis.units"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "Note that indexes cannot store PintArrays, so don't contain unit information"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "print(ax.xaxis.units)"
+   ]
+  },
   {
    "cell_type": "markdown",
    "metadata": {},

diff --git a/pint/__init__.py b/pint/__init__.py
@@ -11,8 +11,6 @@
     :license: BSD, see LICENSE for more details.
 """
 
-import sys
-
 from .context import Context
 from .errors import (  # noqa: F401
     DefinitionSyntaxError,
@@ -36,17 +34,6 @@
     # Backport for Python < 3.8
     from importlib_metadata import version
 
-try:
-    from pint_pandas import PintArray, PintType
-
-    del PintType
-    del PintArray
-
-    _HAS_PINT_PANDAS = True
-except ImportError:
-    _HAS_PINT_PANDAS = False
-    _, _pint_pandas_error, _ = sys.exc_info()
-
 try:  # pragma: no cover
     __version__ = version("pint")
 except Exception:  # pragma: no cover