{
 "cells": [
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "# Modify field data, by adding a white noise to it\n",
    "\n",
    "and visualization of differences as (DCT) variance spectrum plot"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {
    "execution": {
     "iopub.execute_input": "2025-01-13T11:34:05.596532Z",
     "iopub.status.busy": "2025-01-13T11:34:05.596031Z",
     "iopub.status.idle": "2025-01-13T11:34:06.133825Z",
     "shell.execute_reply": "2025-01-13T11:34:06.133343Z"
    }
   },
   "outputs": [],
   "source": [
    "%matplotlib inline\n",
    "# for figures in notebook\n",
    "\n",
    "# import & initialize epygram\n",
    "import epygram\n",
    "epygram.init_env()\n",
    "\n",
    "import os\n",
    "INPUTS_DIR = os.path.join('..', 'inputs')"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {
    "execution": {
     "iopub.execute_input": "2025-01-13T11:34:06.136088Z",
     "iopub.status.busy": "2025-01-13T11:34:06.135838Z",
     "iopub.status.idle": "2025-01-13T11:34:08.335561Z",
     "shell.execute_reply": "2025-01-13T11:34:08.335060Z"
    }
   },
   "outputs": [],
   "source": [
    "r = epygram.open(os.path.join(INPUTS_DIR, 'ICMSHAROM+0022'), 'r')\n",
    "t59 = r.readfield('S059TEMPERATURE')\n",
    "t59.sp2gp()"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {
    "execution": {
     "iopub.execute_input": "2025-01-13T11:34:08.337537Z",
     "iopub.status.busy": "2025-01-13T11:34:08.337354Z",
     "iopub.status.idle": "2025-01-13T11:34:08.524006Z",
     "shell.execute_reply": "2025-01-13T11:34:08.523527Z"
    }
   },
   "outputs": [],
   "source": [
    "# initial field\n",
    "sp59 = t59.dctspectrum()\n",
    "sp59.name = t59.fid['FA']"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {
    "execution": {
     "iopub.execute_input": "2025-01-13T11:34:08.526156Z",
     "iopub.status.busy": "2025-01-13T11:34:08.525909Z",
     "iopub.status.idle": "2025-01-13T11:34:08.627364Z",
     "shell.execute_reply": "2025-01-13T11:34:08.626814Z"
    }
   },
   "outputs": [],
   "source": [
    "# add a white noise\n",
    "import numpy\n",
    "field_data = t59.getdata()\n",
    "noise = numpy.random.normal(0, size=field_data.shape)\n",
    "t59.setdata(field_data + noise)\n",
    "# and compute DCT spectrum\n",
    "sp59n = t59.dctspectrum()\n",
    "sp59n.name = sp59.name + '(noised)'"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {
    "execution": {
     "iopub.execute_input": "2025-01-13T11:34:08.629073Z",
     "iopub.status.busy": "2025-01-13T11:34:08.628914Z",
     "iopub.status.idle": "2025-01-13T11:34:09.288090Z",
     "shell.execute_reply": "2025-01-13T11:34:09.287390Z"
    }
   },
   "outputs": [],
   "source": [
    "# and plot\n",
    "fig, ax = epygram.spectra.plotspectra([sp59, sp59n])"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": []
  }
 ],
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