My trig students are reviewing functions a bit right now. I used this piece of a chart showing average height by country that I found on Wikipedia to build the idea that functions and relations don’t only exist in the isolated world of equations and numbers. By assigning numerical values to information in a chart, you can turn just about any info into a mathematical function, or at least a relation.
We first assigned numbers to the countries of origin (1-11) so that we could have an input value instead of an input country. Using the male data seemed simpler because of it’s proximity to the list of countries, and had the added benefit of the four N/A entries, so we could talk about whether the input 2 (Argentina) were really part of the domain if no output value exists for it.
We listed the domain and range, illustrated the mapping of input values onto output values, listed ordered pairs, and graphed them.
Viewing a chart as a function was a stretch for some (especially whenever I used the word input–“Input? What are we putting it into?”), but is a step toward breaking math out of isolation and realizing its contented existence beyond the classroom.