{
 "cells": [
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "# Image"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "import hvplot.xarray  # noqa"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "import xarray as xr\n",
    "\n",
    "ds = xr.tutorial.open_dataset('air_temperature')\n",
    "ds"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "When data values are available on an x, y grid, they can often be represented as an `image`."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "ds.hvplot.image()"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "This is equivalent to specifying:"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "ds.hvplot.image(x='lon', y='lat', z='air', groupby='time', cmap='kbc_r')"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "A simpler case would be to take the temperature at just one day. Here we'll show how to use `clabel` to control the colorbar and also demonstrate how when the data are symmetric around 0, the \"coolwarm\" colormap is used by default."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "time = '2014-01-01'\n",
    "data = ds.sel(time=time).mean('time') - 273  # convert to celsius\n",
    "\n",
    "data.hvplot.image(x='lon', y='lat', z='air', title=time, clabel='T [C]')"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "We can also override the colorbar ticks and labels with `cticks`, specified as an integer, list of ticks positions, or list of tuples of the tick positions and labels."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "data.hvplot.image(x='lon', y='lat', z='air', title=time, clabel='T [C]', cticks=[(-40, \"Below Freezing\"), (0, \"Freezing\"), (40, \"Above Freezing\")])"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Geographic Data\n",
    "\n",
    "By setting `coastline=True`, we can add a coastline feature to the plot and coerce it to the proper aspect."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "data.hvplot.image(coastline=True)"
   ]
  }
 ],
 "metadata": {
  "language_info": {
   "name": "python",
   "pygments_lexer": "ipython3"
  }
 },
 "nbformat": 4,
 "nbformat_minor": 4
}