Identification with DAGs: Introduction with simple simulations
En español
In this post I want to share with you some introductory ideas on how Directed Acyclical Graphs (DAGs) are used for causal identification. I am also sharing a few (Stata based) numerical simulations (here), that can be illustrative of their use in a regression application.
The DAG approach has been around for at least a decade now, and is described in extent in the excellent book by Pearl and Mackenzie (2018)’s “The Book of Why”. There’s so much going on in the book that I will be writing more about it in a future post.
Notes on Matching in Entrepreneurial Finance Networks
español We are glad our paper (with Virginia Sarria Allende and Gabriela Robiolo) went out in Venture Capital : A International Entrepreneurial Finance Journal. A working paper version is available here. Here are some brief comments on the ideas, the econometrics, and data approach: In the paper we study the “matching” between investors and startups in the entrepreneurial finance market. Broadly speaking, we are concerned with the question of who will invest in who, and in the role played by (social, professional) networks in the explanation. Specifically, we show evidence on a simple idea: due to information related frictions in the entrepreneurial finance market, being closer in the network of connections actually matters for matching. Being closer increases not only the attractiveness of a prospective match, but also makes observable attributes more attractive. But “being closer” has a particular interpretation here. Our measured networked connections, are not the typical social (or follower) style of connections. We recognize a link if there is information that you have worked, invested, mentored, etc. a common startup or organization in the past. So we could say that these are really costly (or “signally meaningful”, in Spence’s sense) connections. For founders (or prospective investors alike)…
Mapping with geopandas and basemapping with contextily
I find the geopandas library to be really useful for mapping with layers. Contextily is also a nice library that allows adding a background basemap. Using them together makes it fairly simple to visualize shapes such as polygons and points, together with contextual mapping information, such as in the following figure: Basemaps are drawn from OpenStreetMap under CC BY SA and map tiles are from Stamen Design, under CC BY 3.0. There are some options for tile design. View the code on Gist. If embedded notebook does not render try here
Tanchella @CIBSE 2017
In english Hoy presentamos nuestra herramienta Tanchella en CIBSE 2017. Tanchella es una herramienta para la recolección y el análisis de datos de redes complejas (sociales, profesionales y financieras) que conforman los ecosistemas de emprendimientos. Este es un desarrollo con fin académico, que nos permite investigar los distintos efectos que tienen estas redes en los mercados de financiamiento de startups. Tanchella es el resultado de un trabajo multidisciplinario, donde participan investigadores y estudiantes de la Universidad Austral, incluyendo la Facultad de Ingeniería, el IAE Business School, y la Facultad de Ciencias Empresariales. Esta presentación hace foco en las cuestiones tecnológicas y algunos resultados. Aquí están los slides.
Table of Differences in Means Tests / Tabla de Tests de Diferencias de Medias
español In this post I leave you a simple Stata code that generates a table of means differences (between 2 groups) for a set of variables. It looks like this: A table of this type will be useful, for example, when the aim is to compare a treatment group and a control group across a series of variables. Stata has the ttest command to perform tests of this kind, but does not incorporate, as far as I know, a functionality for exporting a table of multiple tests. This code tests a large number of variables, with the advantage that it generates and exports a publication-style table. The table is saved in a text (.txt) file. Then, I usually import this table into Excel (insert> data> text) for final retouching before copying it to the final document. I leave you the Excel template as well. For simplicity, asterisks for significant statistics, parentheses and brackets are added – also automatically – by the Excel template. From the statistical point of view, it might be worth mentioning the subject of false-discovery rates, which could be relevant in an application of this type. I will leave it for for a future post. You can test the code…
Using loops to run (and export) many regressions / Usando loops para correr (y exportar) múltiples regresiones
español The use of loops becomes essential when needing to perform repetitive calculations. Looping has many advantages, for example, when needing to do corrections in all the calculations specifications. So here are some interesting features that you would like to do when implementing a loop to run many regressions, and export their outputs: Choose the appropriate method for the regression according to the type of dependent variable. For instance, you might want to estimate the model using OLS (regress) when the dependent variable is continuous and or a probit or a logit model when it is discrete (a dummy variable). Progressively add explanatory variables to the model and export all the output in a single table. This can be done using outreg2 ‘s replace and append options, but if you want instead to write a single command line inside a loop you will have to make the appropriate changes. So assume that you want to estimate a number of econometric models that are quite similar in terms of the explanatory variables that are incorporated, but differ between them in terms of the dependent variables, for example : Model 1: outcome1=b1*x1+b2*x2+b3*X3+b4*X4+e Model 2: outcome2=b1*x1+b2*x2+b3*X3+b4*X4+e In addition you also want to progressively add sets of explanatory variables. So for instance you…
Importing text files into Excel Part II / Importar archivos de texto al Excel Parte II
español For those who find useful to transfer the output of their statistics and regressions to Excel, here is another macro that might be useful. As in the last case, imagine that you are dealing with many tables of statistics and regressions that you have computed with Stata, and you will find useful to take them all to Excel. Such a thing might be useful for visualization, comparing statistics (robustness checks), formatting the tables for presentations or publications, elaborating further graphics, and so on. Building on the macro presented in the previous post, this time I built another one to deal with importing multiple files simultaneously. To see how it works, imagine, as an example, that you have 5 key variables that you are analysing and for each of them you have produced 4 tables (corresponding, for example to different estimation methods) and exported each respectively to a text file. That gives a total of 20 tables to be imported from Excel. First, it might be useful to organize the text files information in a table in Excel as shown in the table below: Using the information in the previous table, the multipletextload macro will : i. Generate a new…