### Invoke Stata from Python

- Call Stata using stata, mata, and pystata magic commands
- Call Stata using a suite of API functions
- Use the magic commands and API functions together with the Stata Function Interface (sfi) module
### Use Python and Stata together

- Access Stata and Mata from Jupyter Notebook, Jupyter Lab, and other environments that support the IPython kernel
- Push Stata data and results to Python and vice versa
- Combine the capabilities of Stata and Python in a single environment

Jupyter Notebook is a powerful and easy-to-use web application that allows you to combine executable code, visualizations, mathematical equations and formulas, narrative text, and other rich media in a single document (a "notebook") for interactive computing and developing. Jupyter notebooks have been widely used by researchers and scientists to share their ideas and results for collaboration and innovation.

Now, you can invoke Stata and Mata from Jupyter Notebooks with the IPython (interactive Python) kernel, meaning you can combine the capabilities of both Python and Stata in a single environment to make your work easily reproducible and shareable with others.

In Jupyter Notebook, you can use two set of tools provided by the pystata Python package to interact with Stata:

- Three IPython (interactive Python) magic commands: stata, mata, and pystata
- A suite of API functions

Before showing you how to use these tools, we configure the **pystata** package. Suppose you have Stata installed in **C:\Program Files\Stata17\** and you use the **Stata/MP** edition. Stata can be initialized as follows:

In [1]:

import stata_setup

stata_setup.config("C:/Program Files/Stata17", "mp")

___ ____ ____ ____ ____ © /__ / ____/ / ____/ 17.0 ___/ / /___/ / /___/ MP—Parallel Edition Statistics and Data Science Copyright 1985-2021 StataCorp LLC StataCorp 4905 Lakeway Drive College Station, Texas 77845 USA 800-STATA-PC https://www.stata.com 979-696-4600 stata@stata.com Stata license: 10-user 4-core network perpetual Serial number: 1 Licensed to: Stata Developer StataCorp LLC Notes: 1. Unicode is supported; see help unicode_advice. 2. More than 2 billion observations are allowed; see help obs_advice. 3. Maximum number of variables is set to 5,000; see help set_maxvar. .

If you get output similar to what is shown above for your edition of Stata, it means that everything is configured properly; see Configuration for more ways to configure **pystata**.

The stata magic is used to execute Stata commands in an IPython environment. In a notebook cell, we put Stata commands underneath the **%%stata** cell magic to direct the cell to call Stata. The following commands load the **auto** dataset and summarize the **mpg** variable. The Stata output is displayed underneath the cell.

In [2]:

%%stata

sysuse auto, clear

summarize mpg

. sysuse auto, clear (1978 automobile data) . summarize mpg Variable | Obs Mean Std. dev. Min Max -------------+--------------------------------------------------------- mpg | 74 21.2973 5.785503 12 41 .

Stata's graphs can also be displayed in the IPython environment. Here we create a scatterplot of car mileage against price by using the **%stata** line magic.

In [3]:

%stata scatter mpg price

Next, we load Python data into Stata, perform analyses in Stata, and then pass Stata returned results to Python for further analysis, using the Second National Health and Nutrition Examination Survey (NHANES II; McDowell et al. 1981).

NHANES II, a dataset concerning health and nutritional status of adults and children in the US, contains 10,351 observations and 58 variables and is stored in a CSV file called nhanes2.csv. Among hese variables is an indicator variable for hypertension (**highbp**) and the continuous variables **age** and **weight**.

We use pandas method **read_csv()** to read the data from the .csv file into a pandas dataframe named **nhanes2**.

In [4]:

import pandas as pd

import io

import requests

data = requests.get("https://www.stata.com/python/pystata/misc/nhanes2.csv").content

nhanes2 = pd.read_csv(io.StringIO(data.decode("utf-8")))

nhanes2

Out [4]:

We load the dataframe into Stata by specifying the -d argument of the **%%stata** magic, and then within Stata, we fit a logistic regression model using **age**, **weight**, and their interaction as predictors of the probability of hypertension. We also push Stata's estimation results displayed by **ereturn list**, including the coefficient vector **e(b)** and variance–covariance matrix **e(V)**, into a Python dictionary called **myeret** by specifying the -eret argument.

In [5]:

%%stata -d nhanes2 -eret myeret

logistic highbp c.age##c.weight

ereturn list

. logistic highbp c.age##c.weight Logistic regression Number of obs = 10,351 LR chi2(3) = 2381.23 Prob > chi2 = 0.0000 Log likelihood = -5860.1512 Pseudo R2 = 0.1689 ------------------------------------------------------------------------------ highbp | Odds ratio Std. err. z P>|z| [95% conf. interval] -------------+---------------------------------------------------------------- age | 1.108531 .0080697 14.15 0.000 1.092827 1.12446 weight | 1.081505 .005516 15.36 0.000 1.070748 1.092371 | c.age#| c.weight | .9992788 .0000977 -7.38 0.000 .9990873 .9994703 | _cons | .0002025 .0000787 -21.89 0.000 .0000946 .0004335 ------------------------------------------------------------------------------ Note: _cons estimates baseline odds. . ereturn list scalars: e(rank) = 4 e(N) = 10351 e(ic) = 4 e(k) = 4 e(k_eq) = 1 e(k_dv) = 1 e(converged) = 1 e(rc) = 0 e(ll) = -5860.151218806021 e(k_eq_model) = 1 e(ll_0) = -7050.765484416371 e(df_m) = 3 e(chi2) = 2381.2285312207 e(p) = 0 e(N_cdf) = 0 e(N_cds) = 0 e(r2_p) = .1688631210670459 macros: e(cmdline) : "logistic highbp c.age##c.weight" e(cmd) : "logistic" e(predict) : "logistic_p" e(estat_cmd) : "logit_estat" e(marginsok) : "default Pr" e(marginsnotok) : "stdp DBeta DEviance DX2 DDeviance Hat Number Resi.." e(title) : "Logistic regression" e(chi2type) : "LR" e(opt) : "moptimize" e(vce) : "oim" e(user) : "mopt__logit_d2()" e(ml_method) : "d2" e(technique) : "nr" e(which) : "max" e(depvar) : "highbp" e(properties) : "b V" matrices: e(b) : 1 x 4 e(V) : 4 x 4 e(mns) : 1 x 4 e(rules) : 1 x 4 e(ilog) : 1 x 20 e(gradient) : 1 x 4 functions: e(sample) .

We can access **e(b)** and **e(V)** by typing myeret['e(b)'] and myeret['e(V)'], respectively, in Python. They are stored in NumPy arrays.

In [6]:

myeret ['e(b)'], myeret['e(V)']

(array([[ 1.03035513e-01, 7.83537342e-02, -7.21492384e-04, -8.50485078e+00]]), array([[ 5.29930771e-05, 3.50509317e-05, -6.97861002e-07, -2.69423163e-03], [ 3.50509317e-05, 2.60132664e-05, -4.74084051e-07, -1.94299575e-03], [-6.97861002e-07, -4.74084051e-07, 9.55811835e-09, 3.50377699e-05], [-2.69423163e-03, -1.94299575e-03, 3.50377699e-05, 1.50887842e-01]]))

We use margins and marginsplot to graph predictions over **age**, which more clearly illustrates the relationship between **age** and the probability of hypertension.

In [7]:

%%stata

quietly margins, at(age=(20(10)80))

marginsplot

. quietly margins, at(age=(20(10)80)) . marginsplot Variables that uniquely identify margins: age .

We use **margins** to estimate the predicted probability of hypertension for all combinations of **age** and **weight** for values of **age** ranging from 20 to 80 years in increments of 5 and for values of **weight** ranging from 40 to 180 kilograms in increments of 5. The option **saving(predictions, replace)** saves the predictions to a dataset named **predictions.dta**. Our goal is to use Python to create a three-dimensional surface plot of those predictions.

The dataset **predictions.dta** contains the variables **_at1** and **_at2**, which correspond to the values of **age** and **weight** that we specified in the **at()** option. The dataset also contains the variable **_margin**, which is the marginal prediction of the probability of high blood pressure. We rename those variables to **age**, **weight**, and **pr_highbp** respectively.

Lastly we store the dataset in Stata as a pandas dataframe named **preddata** in Python by specifying the -doutd argument.

In [8]:

%%stata -doutd preddata

quietly margins, at(age=(20(5)80) weight=(40(5)180))

saving(predictions, replace)

use predictions, clear

list _at1 _at2 _margin in 1/5

rename _at1 age

rename _at2 weight

rename _margin pr_highbp

. quietly margins, at(age=(20(5)80) weight=(40(5)180)) /// > saving(predictions, replace) . . use predictions, clear (Created by command margins; also see char list) . list _at1 _at2 _margin in 1/5 +------------------------+ | _at1 _at2 _margin | |------------------------| 1. | 20 40 .0200911 | 2. | 20 45 .0274497 | 3. | 20 50 .0374008 | 4. | 20 55 .0507709 | 5. | 20 60 .0685801 | +------------------------+ . rename _at1 age . rename _at2 weight . rename _margin pr_highbp .

We list the first five observations of the **age**, **weight**, **pr_highbp** columns within the dataframe.

In [9]:

preddata[['age', 'weight', 'pr_highbp']].head()

Out [9]:

Next we use Python to create a three-dimensional surface plot. First, we set the graph size to be 10 by 8 inches using the **figure()** method in the **pyplot** module of the Matplotlib package. We use the **axes()** method to define a three-dimensional set of axes named **ax** and draw the surfrace plot with the **plot_trisurf()** method. Next we set the ticks and labels for the x, y, and z axes. Last, we adjust the elevation and azimuth of the plot.

In [11]:

import matplotlib.pyplot as plt

import numpy as np

# define the axes

fig = plt.figure(1, figsize=(10, 8))

ax = plt.axes(projection='3d')

# plot

ax.plot_trisurf(preddata['age'], preddata['weight'], preddata['pr_highbp'],cmap=plt.cm.Spectral_r)

# set ticks and labels for x, y, and z axes

ax.set_xticks(np.arange(20, 90, step=10))

ax.set_yticks(np.arange(40, 200, step=40))

ax.set_zticks(np.arange( 0, 1.2, step=0.2))

ax.set_xlabel(Age (years)")

ax.set_ylabel(Weight (kg)")

ax.set_zlabel(Probability of Hypertension")

# adjust the view angle

ax.view_init(elev=30, azim=240)

# show the plot

plt.show()

We have demonstrated how to access Stata from Python, but you can also access Mata from Python using the **mata** magic; see The mata magic and Example 4: Work with Mata.

We can also interact with Stata by using a suite of functions defined in the config and stata modules from the **pystata** Python package. We will demonstrate how to use these API functions to interact with Stata as an alternative to the **%%stata** magic command.

We import the **stata** module from **pystata**. Then call the pdataframe_to_data() method to load the pandas dataframe **nhanes2** into Stata and call the run() method to fit the logistic regression model.

In [12]:

from pystata import stata

stata.pdataframe_to_data(nhanes2, force=True)

stata.run('logistic highbp c.age##c.weight')

Logistic regression Number of obs = 10,351 LR chi2(3) = 2381.23 Prob > chi2 = 0.0000 Log likelihood = -5860.1512 Pseudo R2 = 0.1689 ------------------------------------------------------------------------------ highbp | Odds ratio Std. err. z P>|z| [95% conf. interval] -------------+---------------------------------------------------------------- age | 1.108531 .0080697 14.15 0.000 1.092827 1.12446 weight | 1.081505 .005516 15.36 0.000 1.070748 1.092371 | c.age#| c.weight | .9992788 .0000977 -7.38 0.000 .9990873 .9994703 | _cons | .0002025 .0000787 -21.89 0.000 .0000946 .0004335 ------------------------------------------------------------------------------ Note: _cons estimates baseline odds.

Then we use the get_ereturn() method to store the **e()** results returned by the **logistic** command in Python as a dictionary named **myeret2** and display **e(b)** and **e(V)** within it.

In [13]:

myeret2 = stata.get_ereturn()

myeret2['e(b)'], myeret2['e(V)']

Out [13]:

(array([[ 1.03035513e-01, 7.83537342e-02, -7.21492384e-04, -8.50485078e+00]]), array([[ 5.29930771e-05, 3.50509317e-05, -6.97861002e-07, -2.69423163e-03], [ 3.50509317e-05, 2.60132664e-05, -4.74084051e-07, -1.94299575e-03], [-6.97861002e-07, -4.74084051e-07, 9.55811835e-09, 3.50377699e-05], [-2.69423163e-03, -1.94299575e-03, 3.50377699e-05, 1.50887842e-01]]))

Next we call the **run()** method to estimate the predicted probability of hypertension for all combinations of **age** and **weight**, save the prediction results in a dataset named **predictions.data**, and load the dataset into Stata and rename the variables.

In [14]:

stata.run('''

quietly margins, at(age=(20(5)80) weight=(40(5)180)) ///

saving(predictions, replace)

use predictions, clear

list _at1 _at2 _margin in 1/5

rename _at1 age

rename _at2 weight

rename _margin pr_highbp

''')

. . quietly margins, at(age=(20(5)80) weight=(40(5)180)) /// > saving(predictions, replace) . . use predictions, clear (Created by command margins; also see char list) . list _at1 _at2 _margin in 1/5 +------------------------+ | _at1 _at2 _margin | |------------------------| 1. | 20 40 .0200911 | 2. | 20 45 .0274497 | 3. | 20 50 .0374008 | 4. | 20 55 .0507709 | 5. | 20 60 .0685801 | +------------------------+ . rename _at1 age . rename _at2 weight . rename _margin pr_highbp .

We call the pdataframe_from_data() function in the **stata** module to store the **age**, **pr_highbp** in current dataset to a pandas dataframe named **preddata2**.

In [15]:

preddata2 = stata.pdataframe_from_data(var="age weight pr_highbp")

preddata2.head()

Out [15]:

Once we have this dataframe, we can create the same three-dimensional surface plot as above.

Note that you can also use the Stata Function Interface (sfi) module to access Stata's core features. The combination of those tools makes it much easier to interact with Stata from Jupyter Notebook; see Example 5: Call Stata using API functions for an example.

Hunter, J. D. 2007. Matplotlib: A 2D Graphics Environment. *Computing in Science & Engineering* 9: 90–95.

McDowell, A., A. Engel, J. T. Massey, and K. Maurer. 1981. Plan and operation of the Second National Health and Nutrition Examination Survey, 1976–1980. *Vital and Health Statistics* 1(15): 1–144.

Mckinney, W. 2010. Data Structures for Statistical Computing in Python. *Proceedings of the 9th Python in Science Conference*, 56–61. (publisher link).

Oliphant, T. E. 2006. *A Guide to NumPy*, 2nd ed. Austin, TX: Continuum Press.

Péz, F., and B. E. Granger. 2007. IPython: A System for Interactive Scientific Computing, *Computing in Science and Engineering* 9: 21–29. DOI:10.1109/MCSE.2007.53 (publisher link)

Learn more about Stata's programming features.

Read more about how to call Stata from Python in the *Stata Programming Reference Manual*; see [P] PyStata module.

Read more about the **pystata** Python package.

Read more about how to call Python from Stata in the *Stata Programming Reference Manual*; see [P] PyStata integration.

Read more about the **Stata Function Interface** (sfi) Python module.