Next: Testing `print-graph`

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The final version is different from what we planned in two ways: first, it contains additional values calculated once in the varlist; second, it carries an option to specify the labels’ increment per row. This latter feature turns out to be essential; otherwise, a graph may have more rows than fit on a display or on a sheet of paper.

This new feature requires a change to the `Y-axis-column`

function, to add `vertical-step`

to it. The function looks like
this:

```
;;; Final version.
(defun Y-axis-column
(height width-of-label &optional vertical-step)
"Construct list of labels for Y axis.
HEIGHT is maximum height of graph.
WIDTH-OF-LABEL is maximum width of label.
VERTICAL-STEP, an option, is a positive integer
that specifies how much a Y axis label increments
for each line. For example, a step of 5 means
that each line is five units of the graph."
```

(let (Y-axis (number-per-line (or vertical-step 1))) (while (> height 1) (if (zerop (% height Y-axis-label-spacing))

```
;; Insert label.
(setq Y-axis
(cons
(Y-axis-element
(* height number-per-line)
width-of-label)
Y-axis))
```

```
;; Else, insert blanks.
(setq Y-axis
(cons
(make-string width-of-label ? )
Y-axis)))
(setq height (1- height)))
```

```
;; Insert base line.
(setq Y-axis (cons (Y-axis-element
(or vertical-step 1)
width-of-label)
Y-axis))
(nreverse Y-axis)))
```

The values for the maximum height of graph and the width of a symbol
are computed by `print-graph`

in its `let`

expression; so
`graph-body-print`

must be changed to accept them.

```
;;; Final version.
(defun graph-body-print (numbers-list height symbol-width)
"Print a bar graph of the NUMBERS-LIST.
The numbers-list consists of the Y-axis values.
HEIGHT is maximum height of graph.
SYMBOL-WIDTH is number of each column."
```

(let (from-position) (while numbers-list (setq from-position (point)) (insert-rectangle (column-of-graph height (car numbers-list))) (goto-char from-position) (forward-char symbol-width)

;; Draw graph column by column. (sit-for 0) (setq numbers-list (cdr numbers-list))) ;; Place point for X axis labels. (forward-line height) (insert "\n")))

Finally, the code for the `print-graph`

function:

```
;;; Final version.
(defun print-graph
(numbers-list &optional vertical-step)
"Print labeled bar graph of the NUMBERS-LIST.
The numbers-list consists of the Y-axis values.
```

Optionally, VERTICAL-STEP, a positive integer, specifies how much a Y axis label increments for each line. For example, a step of 5 means that each row is five units."

```
(let* ((symbol-width (length graph-blank))
;;
````height`

is both the largest number
;; and the number with the most digits.
(height (apply 'max numbers-list))

```
(height-of-top-line
(if (zerop (% height Y-axis-label-spacing))
height
;; else
(* (1+ (/ height Y-axis-label-spacing))
Y-axis-label-spacing)))
```

(vertical-step (or vertical-step 1)) (full-Y-label-width (length

(concat (number-to-string (* height-of-top-line vertical-step)) Y-axis-tic))))

(print-Y-axis height-of-top-line full-Y-label-width vertical-step)

(graph-body-print numbers-list height-of-top-line symbol-width) (print-X-axis numbers-list)))

Next: Testing `print-graph`

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