Tidyquant is a nifty R package for get stock-price data.

Blair Fix

They say that knowledge is power. Well, in capitalism, knowledge is also
money ... but only if you keep it under lock and key. Hence, researchers
who study capitalism are often faced with a dilemma: the best data is
kept behind a hefty paywall. The only way to get access is if your
institution pays for a subscription. And if you're not lucky enough to
work for a university, you're out of luck.

Given this problem, I'm always on the look out for open-access data, and
for tools that facilitate access to said data. This week I discovered an
R package called
['Tidyquant'](https://www.rdocumentation.org/packages/tidyquant/versions/1.0.3){target="_blank"
rel="noopener"} that does a nice job of giving access to stock market
data (which it pulls from Yahoo Finance).

Here's a brief tutorial. Install Tidyquant with this command:

    install.packages('tidyquant')

Then load it:

    library(tidyquant)

Next, find the stock ticker for the company you want to look up. As an
example, let's do Exxon Mobile, who's ticker is XOM. The code below will
pull daily Exxon stock prices from the beginning of 1990 to today.

    getSymbols("XOM", 
               from = '1990-01-01',
               to = today(),
               warnings = FALSE,
               auto.assign = TRUE
    )

The function returns a table called `XOM` that looks like this:

<figure class="wp-block-image size-large">
<img
src="https://i0.wp.com/economicsfromthetopdown.com/wp-content/uploads/2021/09/xom_table.png?w=723&amp;ssl=1"
decoding="async" data-recalc-dims="1" />
</figure>

That's pretty nifty. Let's plot some of the data. To plot the closing
price, we enter:

    plot(XOM$XOM.Close)

Here's what the plot looks like. It's not something I'd publish. But
it's good enough to explore the data.

<figure class="wp-block-image size-large">
<img
src="https://i0.wp.com/economicsfromthetopdown.com/wp-content/uploads/2021/09/xom_close.png?w=723&amp;ssl=1"
decoding="async" data-recalc-dims="1" />
</figure>

Suppose we want to compare Exxon's stock price to the S&P 500. That's
easy enough. On Yahoo Finance, the S&P 500 symbol is \^GSPC. Plug that
into our function:

    getSymbols("^GSPC", 
               from = '1990-01-01',
               to = today(),
               warnings = FALSE,
               auto.assign = TRUE
    )

You'll get a table called `GSPC` containing daily data for S&P 500
prices.

<figure class="wp-block-image size-large">
<img
src="https://i0.wp.com/economicsfromthetopdown.com/wp-content/uploads/2021/09/gspc_table.png?w=723&amp;ssl=1"
decoding="async" data-recalc-dims="1" />
</figure>

Next, let's do some simple differential analysis. Let's see how Exxon's
stock price has changed relative to the S&P 500. That's another one
liner:

    plot(XOM$XOM.Close / GSPC$GSPC.Close)

Here's the result, the ratio of Exxon's price to the S&P 500:

<figure class="wp-block-image size-large">
<img
src="https://i0.wp.com/economicsfromthetopdown.com/wp-content/uploads/2021/09/xom_gspc.png?w=723&amp;ssl=1"
decoding="async" data-recalc-dims="1" />
</figure>

As you can see, Exxon hasn't been doing so well since oil prices peaked
in 2008.

Tidyquant is a nifty little tool that gives you quick access to Yahoo
Finance data. While it's no replacement for the paywalled data that is
closely guarded by Bloomberg and the likes, it's a decent package for
doing exploratory research.

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They say that knowledge is power. Well, in capitalism, knowledge is also money … but only if you keep it under lock and key. Hence, researchers who study capitalism are often faced with a dilemma: the best data is kept behind a hefty paywall. The only way to get access is if your institution pays for a subscription. And if you’re not lucky enough to work for a university, you’re out of luck.

Postagens de Rogue Scholar

Tidyquant: An Open-Access Tool for Studying the Stock Market