Lessons/Lesson20_Numpy_Intro.ipynb

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    "# Introduction to Numpy\n",
    "\n",
    "RECAP: You have previously learned how to manipulate data with the `pandas` library. \n",
    "\n",
    "Today, we will be learning how to perform calculations with another library known as __`numpy`.__ `numpy` allows you to do math on entire lists of data, all at the same time!"
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    "Let's __create a list containing the numbers 0 through 5__ and assign it to a variable:"
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    "# Create a list containing the numbers 0 through 4\n",
    "\n",
    "\n",
    "# or convert the range to a list\n"
   ]
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   "source": [
    "# let's see what it looks like\n"
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    "Using lists can be really useful, because you can store any set of data in the list.\n",
    "\n",
    "Now, lets __add 1 to each of the items in the list.__ Is there a simple way to do this?"
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   "source": [
    "data + 1"
   ]
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    "hmm ... that didn't work! That is because __the `+` operator acts as a concatenation operator__ on lists, and we learned previously that we can only concatenate lists with lists, not with integers. \n",
    "\n",
    "Another way we could update our list is to add 1 to each of the items in the list individually. We can do this by **indexing to isolate each value** in the list one by one. "
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   "source": [
    "# Add 1 to each item in the array you created above\n",
    "\n",
    "\n",
    "# print the list to see how it changed\n"
   ]
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    "__This is very inconvenient with a list.__ It is more useful with a single number, where you can do something like this to add a number:"
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    "# create a single variable and add a number to it\n"
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   "source": [
    "Today we will be using __`numpy`__, which allows us to quickly and efficiently perform mathematical operations on entire lists (or, as they're called in __`numpy`__, *arrays*)!"
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   "source": [
    "First we will __import `numpy`.__ Remember when we imported `pandas`, we gave it the special nickname `pd`? We're also going to give `numpy` a nickname: __`np`__:"
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   "source": [
    "# Load numpy\n"
   ]
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    "Now whenever we type __`np`, python will know we really mean `numpy`.__\n",
    "\n",
    "There is a ton of useful stuff we can do with `numpy`, so let's __redo the example above using `numpy` `arrays`__ instead of `lists`."
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    "# create a numpy array containing the numbers 0 through 4\n",
    "\n",
    "# you can print arrays just like lists\n",
    "\n",
    "\n"
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    "Numpy `arrays` act very similarly to regular python `lists`, __we can grab individual items using the same syntax:__"
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    "# Print any number from the numpy array you just created:\n"
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    "Numpy `arrays` also add a lot of useful features such as the ability to perform commands __*on all items in a list at the same time*.__\n",
    "\n",
    "We can demonstrate this by __adding a number to all of the items in the Numpy `array`__:"
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    "# Add any number to the array we created above\n",
    "\n",
    "# print the array\n"
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   "source": [
    "See how much easier that was than manually changing each element of a list? We will be using `numpy` a lot to perform calculations on arrays of data. In the above example we used addition, but you can also perform any mathematical operation we've talked about with `numpy` arrays.\n",
    "\n",
    "In this lesson you learned how to:\n",
    "* Load `numpy` into Python.\n",
    "* Create an `array` with `numpy`.\n",
    "* Perform math with `numpy` arrays.\n",
    "     "
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