Generate probabilities of imprinting to custom subsets of influenza A viruses | Input the custom frequencies into get_imprinting_probabilities()

1. Install the imprinting package | 1.1 Install the devtools package | 1.2 Load the devtools package | 1.3 Install the imprinting package from github | 1.4 Load the imprinting package | 2. Use the package to calculate imprinting probabilities | 2.1 Calculate imprinting probabilities for one country and year of observation | 2.2 Why do we specify the observation_year? | 2.2 View a list of the available countries | 2.3 Generate probabilities for many countries and observation years | 3. Plot the outputs | 3.1 Plot the first country-year combination in the output data frame | Select a specific country and year to plot | 3.2 Plot up to five countires at a time | 4. Explore the underlying data and components of the imprinting probabilities | Get the probability that an individual imprinted 0, 1, 2, ... 12 years after birth