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Reproducing results is an important aspect of any research. First, reproducibility serves as a form of quality assurance. If we pass an analysis project to another person, they should be able to run the entire project from start to finish and obtain the same results. They can critically assess the methodology and code while detecting potential errors. Another goal of reproducibility is enabling the verification of our analysis. When someone else is able to check our results, it ensures the integrity of the analyses by determining that the conclusions are not dependent on a particular person running the code or workflow on a particular day or in a particular environment.

Not only is reproducibility a key component in ethical and accurate research, but it is also a requirement for many scientific journals. For example, the Journal of Survey Statistics and Methodology (JSSAM) and Public Opinion Quarterly (POQ) require authors to make code, data, and methodology transparent and accessible to other researchers who wish to verify or build on existing work.
Not only is reproducibility a key component in ethical and accurate research, but it is also a requirement for many scientific journals. For example, the *Journal of Survey Statistics and Methodology* (JSSAM) and *Public Opinion Quarterly* (POQ) require authors to make code, data, and methodology transparent and accessible to other researchers who wish to verify or build on existing work.

Reproducible research requires that the key components of analysis are available, discoverable, documented, and shared with others. The four main components that we should consider are:

Expand All @@ -20,7 +20,7 @@ Reproducible research requires that the key components of analysis are available
- **Environment**: environment of the project, including the R version, packages, operating system, and other dependencies used in the analysis
- **Methodology**: survey and analysis methodology, including rationale behind sample, questionnaire and analysis decisions, interpretations, and assumptions

In Chapter \@ref(c08-communicating-results), we briefly mention how each of these is important to include in the methodology report and when communicating the findings of a study. However, to be transparent and effective analysts, we need to ensure we not only discuss these through text but also provide files and additional information when requested. Often, when starting a project, we may be eager to jump into the data and make decisions as we go without full documentation. This can be challenging if we need to go back and make changes or understand even what we did a few months ago. It benefits other analysts and potentially our future selves to document everything from the start. The good news is that many tools, practices, and project management techniques make survey analysis projects easy to reproduce. For best results, we should decide which techniques and tools to use before starting a project (or very early on.)
In Chapter \@ref(c08-communicating-results), we briefly mention how each of these is important to include in the methodology report and when communicating the findings of a study. However, to be transparent and effective analysts, we need to ensure we not only discuss these through text but also provide files and additional information when requested. Often, when starting a project, we may be eager to jump into the data and make decisions as we go without full documentation. This can be challenging if we need to go back and make changes or understand even what we did a few months ago. It benefits other analysts and potentially our future selves to document everything from the start. The good news is that many tools, practices, and project management techniques make survey analysis projects easy to reproduce. For best results, we should decide which techniques and tools to use before starting a project (or very early on).

This chapter covers some of our suggestions for tools and techniques we can use in projects. This list is not comprehensive but aims to provide a starting point for those looking to create a reproducible workflow.

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```

\index{here package|(}
In a project-based workflow, all paths are relative and, by default, relative to the folder the `.Rproj` file is located in. By using relative paths, others can open and run our files even if their directory configuration differs from ours (e.g., Mac and Windows users have different directory path structures.) The {here} package enables easy file referencing, and we can start by using the `here::here()` function to build the path for loading or saving data [@R-here]. Below, we ask R to read the CSV file `anes_2020.csv` in the project directory's `data` folder:
In a project-based workflow, all paths are relative and, by default, relative to the folder the `.Rproj` file is located in. By using relative paths, others can open and run our files even if their directory configuration differs from ours (e.g., Mac and Windows users have different directory path structures). The {here} package enables easy file referencing, and we can start by using the `here::here()` function to build the path for loading or saving data [@R-here]. Below, we ask R to read the CSV file `anes_2020.csv` in the project directory's `data` folder:

```{r}
#| label: reprex-project-file-example
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read_csv(here::here("data", "anes2020_clean.csv"))
```

The combination of projects and the {here} package keep all associated files in an organized manner. This workflow makes it more likely that our analyses can be reproduced by us or our colleagues.
The combination of projects and the {here} package keep all associated files organized. This workflow makes it more likely that our analyses can be reproduced by us or our colleagues.
\index{here package|)} \index{R projects|)}

## Functions and packages

We may find ourselves repeating ourselves in our script, and the chance of errors increases whenever we copy and paste our code. By creating a function, we can create a consistent set of commands that reduce the likelihood of mistakes. Functions also organize our code, improve the code readability, and allow others to execute the same commands. For example, in Chapter \@ref(c13-ncvs-vignette), we create a function to run sequences of `rename()`, `filter()`, `group_by()`, and summarize statements across different variables. Creating functions helps us avoid overlooking necessary steps.
We may find that we are repeating ourselves in our script, and the chance of errors increases whenever we copy and paste our code. By creating a function, we can create a consistent set of commands that reduce the likelihood of mistakes. Functions also organize our code, improve the code readability, and allow others to execute the same commands. For example, in Chapter \@ref(c13-ncvs-vignette), we create a function to run sequences of `rename()`, `filter()`, `group_by()`, and summarize statements across different variables. Creating functions helps us avoid overlooking necessary steps.

A package is made up of a collection of functions. If we find ourselves sharing functions with others to replicate the same series of commands in a separate project, creating a package can be a useful tool for sharing the code along with data and documentation.

## Version control with Git

\index{Version control|(} \index{Git| see {Version control}}
Often, a survey analysis project produces a lot of code. Keeping track of the latest version can become challenging as files evolve throughout a project. If a team of analysts is working on the same script, someone may use an outdated version, resulting in incorrect results or redundant work.
Often, a survey analysis project produces a lot of code. Keeping track of the latest version can become challenging, as files evolve throughout a project. If a team of analysts is working on the same script, someone may use an outdated version, resulting in incorrect results or redundant work.

Version control systems like Git can help alleviate these pains. Git is a system that tracks changes in files. We can use Git to follow code evaluation and manage asynchronous work. With Git, it is easy to see any changes made in a script, revert changes, and resolve differences between code versions (called conflicts.)
Version control systems like Git can help alleviate these pains. Git is a system that tracks changes in files. We can use Git to follow code evaluation and manage asynchronous work. With Git, it is easy to see any changes made in a script, revert changes, and resolve differences between code versions (called conflicts).

Services such as GitHub or GitLab provide hosting and sharing of files as well as version control with Git. For example, we can visit the [GitHub repository for this book](https://github.com/tidy-survey-r/tidy-survey-book) and see the files that build the book, when they were committed to the repository, and the history of modifications over time.

Expand All @@ -91,14 +91,14 @@ Using version control in analysis projects makes collaboration and maintenance m
\index{renv package|(} \index{Package management|see {renv package}}
Ensuring reproducibility involves not only using version control of code but also managing the versions of packages. If two people run the same code but use different package versions, the results might differ because of changes to those packages. For example, this book currently uses a version of the {srvyr} package from GitHub and not from CRAN. This is because the version of {srvyr} on CRAN has some bugs (errors) that result in incorrect calculations. The version on GitHub has corrected these errors, so we have asked readers to install the GitHub version to obtain the same results.

One way to handle different package versions is with the {renv} package. This package allows researchers to set the versions for each package used and manage package dependencies. Specifically, {renv} creates isolated, project-specific environments that record the packages and their versions used in the code. When initiated by a new user, {renv} checks whether the installed packages are consistent with the recorded version for the project. If not, it installs the appropriate versions so that others can replicate the project's environment to rerun the code and obtain consistent results [@R-renv].
One way to handle different package versions is with the {renv} package. This package allows researchers to set the versions for each used package and manage package dependencies. Specifically, {renv} creates isolated, project-specific environments that record the packages and their versions used in the code. When initiated by a new user, {renv} checks whether the installed packages are consistent with the recorded version for the project. If not, it installs the appropriate versions so that others can replicate the project's environment to rerun the code and obtain consistent results [@R-renv].

\index{renv package|)}

## R environments with Docker

\index{Environment management|(} \index{Docker|see {Environment management}}
Just as different versions of packages can introduce discrepancies or compatibility issues, the version of R can also prevent reproducibility. Tools such as Docker can help with this potential issue by creating isolated environments that define the version of R being used, along with other dependencies and configurations. The entire environment is bundled in a container. The container, defined by a Dockerfile, can be shared so anybody, regardless of their local setup, can run the R code in the same environment.
Just as different versions of packages can introduce discrepancies or compatibility issues, the version of R can also prevent reproducibility. Tools such as Docker can help with this potential issue by creating isolated environments that define the version of R being used, along with other dependencies and configurations. The entire environment is bundled in a container. The container, defined by a Dockerfile, can be shared so that anybody, regardless of their local setup, can run the R code in the same environment.
\index{Environment management|)}

## Workflow management with {targets}
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runif(5)
```

Since the seed is set to `999`, running `runif(5)` multiple times always produces the same output. The choice of the seed number is up to the analyst. For example, this could be the date (`20240102`) or time of day (`1056`) when the analysis was first conducted, a phone number (`8675309`), or the first few numbers that come to mind (`369`.) As long as the seed is set for a given analysis, the actual number is up to the analyst to decide. It is important to note that `set.seed()` should be used **before** random number generation. Run it once per program, and the seed is applied to the entire script. We recommend setting the seed at the beginning of a script, where libraries are loaded.
Since the seed is set to `999`, running `runif(5)` multiple times always produces the same output. The choice of the seed number is up to the analyst. For example, this could be the date (`20240102`) or time of day (`1056`) when the analysis was first conducted, a phone number (`8675309`), or the first few numbers that come to mind (`369`). As long as the seed is set for a given analysis, the actual number is up to the analyst to decide. It is important to note that `set.seed()` should be used **before** random number generation. Run it once per program, and the seed is applied to the entire script. We recommend setting the seed at the beginning of a script, where libraries are loaded.

### Descriptive names and labels

\index{American National Election Studies (ANES)|(}
Using descriptive variable names or labeling data can also assist with reproducible research. For example, in the ANES data, the variable names in the raw data all start with `V20` and are a string of numbers. To make things easier to reproduce in this book, we opted to change the variable names to be more descriptive of what they contained (e.g., `Age`.)\index{American National Election Studies (ANES)|)} This can also be done with the data values themselves. \index{Categorical data|(}\index{Factor|(}One way to accomplish this is by creating factors for categorical data, which can ensure that we know that a value of `1` really means `Female`, for example.\index{Factor|)} There are other ways of handling this, such as attaching labels to the data instead of recoding variables to be descriptive (see Chapter \@ref(c11-missing-data).) \index{Categorical data|)} As with random number seeds, the exact method is up to the analyst, but providing this information can help ensure our research is reproducible.
Using descriptive variable names or labeling data can also assist with reproducible research. For example, in the ANES data, the variable names in the raw data all start with `V20` and are a string of numbers. To make things easier to reproduce in this book, we opted to change the variable names to be more descriptive of what they contained (e.g., `Age`).\index{American National Election Studies (ANES)|)} This can also be done with the data values themselves. \index{Categorical data|(}\index{Factor|(}One way to accomplish this is by creating factors for categorical data, which can ensure that we know that a value of `1` really means `Female`, for example.\index{Factor|)} There are other ways of handling this, such as attaching labels to the data instead of recoding variables to be descriptive (see Chapter \@ref(c11-missing-data)). \index{Categorical data|)} As with random number seeds, the exact method is up to the analyst, but providing this information can help ensure our research is reproducible.

## Additional resources

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