In parsermd: Formal Parser and Related Tools for R Markdown Documents

Load cache from a latter code chunk

Sometimes we may want to insert an object value early in the document, when the object has not been created. For example, you may want to mention a result in your abstract using an inline R expression, but the result is calculated later in the report.

One solution is to save() the workspace in a .RData file in the end of the document, and load() it in the beginning, e.g.

x = 'NOT YET AVAILABLE'  # an object to be used
if (file.exists('everything.RData')) load('everything.RData')

In the end of the document, you save the workspace:

save.image('everything.RData')

Then you can use `r x` after everything.RData is loaded. When it is not available, you will see x as r x.

The function load_cache() is an alternative solution, which allows you to load the value of an object from a specific code chunk, when the chunk has been cached.

For example, there is no object called y that has been created in this document yet, but we can still insert it here: r knitr::load_cache('test-a', 'y'), as long as it will be created in the code chunk with the label test-a later.

y = 2*pi

The first time you compile the document, you will see y is NOT AVAILABLE, but when you compile it for the second time, you will see its value r y.

You do not have to specify the object name in load_cache(), in which case the database will just be loaded, and you can use any objects available in the database as if they had been computed by the code chunk later.