The letters

After stating its system in brief, the 1446 book explained the letters one class at a time: the initial consonants, the vowels, the final consonants. Each class was explained by the same method.

Part I stated gog’s whole system in brief. This part then explains gog’s letters one class at a time, as the 1446 book did. The marks are the initial consonants: the visible forms, such as a dot, a bar or a line. A mark draws nothing until a position places it. The positions are the vowels: x, y and z. Only edge takes none of them: a layout transform computes its positions instead. Each position has a scale, which decides where a number, a category or a date falls on its axis. The refining channels are the final consonants: color, size, shape, pattern, opacity. Each is optional, and when it is mapped to a column, it gets a legend that shows which value each color, size, shape, pattern or opacity stands for.

Three channels belong to none of these classes: group, label and play. On a line, group makes the same split as color: one line per category. But every line is drawn alike, so group gets no legend. It separates the lines, but nothing on the plot shows how. label gives each text mark the words it draws, rather than refining the mark. play splits the rows into frames and plays them in order, the way a facet splits them into panels. Its chapter is in Part III, The sentences.

The Data chapter opens this part with the table every sentence starts from, because nothing can be drawn until a table is named. The book’s data follows, saying where this book’s own tables come from and how to load one in any of the four languages. Then come the letters themselves. Choosing a mark opens them, and then each mark has a chapter of its own, fourteen in a row from point to edge. After the marks, the Scales chapter covers the scales of the positions x, y and z, and the Channels and legends chapter covers the final consonants and their legends. The Setting vs mapping chapter shows the difference between a column you map and a constant you set. The Transforms chapter closes the part: a transform derives new values from your columns, such as counts, means or a smooth curve. Transforms take more practice than any other kind of word. They are also what let you ask questions of a table instead of only drawing it. The better you know them, the better you can use gog, so read that chapter without hurrying.

Every mark chapter follows the same template, just as the 1446 book explained each letter class by the same method. It says what the mark draws, what it requires, what refines it and which transforms it takes. It then closes with three sections that have the same names in every chapter: What you can set, What it refuses and What comes next. A short summary, In short, may come between the last two. That sameness is deliberate: it is the No Exceptions law applied to this book’s structure. Learning the second mark is faster than learning the first. By the fifth you know which section answers which question, and you can read only the one you need.