Previous: Similarities differences, Up: print-X-axis [Contents][Index]
The first function should print the X axis tic marks. We must specify the tic marks themselves and their spacing:
(defvar X-axis-label-spacing
(if (boundp 'graph-blank)
(* 5 (length graph-blank)) 5)
"Number of units from one X axis label to next.")
(Note that the value of graph-blank is set by another defvar.
The boundp predicate checks whether it has already been set;
boundp returns nil if it has not. If graph-blank were
unbound and we did not use this conditional construction, we would enter the
debugger and see an error message saying ‘Debugger entered--Lisp error: (void-variable graph-blank)’.)
Here is the defvar for X-axis-tic-symbol:
(defvar X-axis-tic-symbol "|" "String to insert to point to a column in X axis.")
The goal is to make a line that looks like this:
| | | |
The first tic is indented so that it is under the first column, which is indented to provide space for the Y axis labels.
A tic element consists of the blank spaces that stretch from one tic to the
next plus a tic symbol. The number of blanks is determined by the width of
the tic symbol and the X-axis-label-spacing.
The code looks like this:
;;; X-axis-tic-element … (concat (make-string ;; Make a string of blanks. (- (* symbol-width X-axis-label-spacing) (length X-axis-tic-symbol)) ? ) ;; Concatenate blanks with tic symbol. X-axis-tic-symbol) …
Next, we determine how many blanks are needed to indent the first tic mark
to the first column of the graph. This uses the value of
full-Y-label-width passed it by the print-graph function.
The code to make X-axis-leading-spaces looks like this:
;; X-axis-leading-spaces … (make-string full-Y-label-width ? ) …
We also need to determine the length of the horizontal axis, which is the length of the numbers list, and the number of ticks in the horizontal axis:
;; X-length … (length numbers-list)
;; tic-width … (* symbol-width X-axis-label-spacing)
;; number-of-X-ticks
(if (zerop (% (X-length tic-width)))
(/ (X-length tic-width))
(1+ (/ (X-length tic-width))))
All this leads us directly to the function for printing the X axis tic line:
(defun print-X-axis-tic-line
(number-of-X-tics X-axis-leading-spaces X-axis-tic-element)
"Print ticks for X axis."
(insert X-axis-leading-spaces)
(insert X-axis-tic-symbol) ; Under first column.
;; Insert second tic in the right spot. (insert (concat (make-string (- (* symbol-width X-axis-label-spacing) ;; Insert white space up to second tic symbol. (* 2 (length X-axis-tic-symbol))) ? ) X-axis-tic-symbol))
;; Insert remaining ticks.
(while (> number-of-X-tics 1)
(insert X-axis-tic-element)
(setq number-of-X-tics (1- number-of-X-tics))))
The line of numbers is equally straightforward:
First, we create a numbered element with blank spaces before each number:
(defun X-axis-element (number)
"Construct a numbered X axis element."
(let ((leading-spaces
(- (* symbol-width X-axis-label-spacing)
(length (number-to-string number)))))
(concat (make-string leading-spaces ? )
(number-to-string number))))
Next, we create the function to print the numbered line, starting with the number 1 under the first column:
(defun print-X-axis-numbered-line
(number-of-X-tics X-axis-leading-spaces)
"Print line of X-axis numbers"
(let ((number X-axis-label-spacing))
(insert X-axis-leading-spaces)
(insert "1")
(insert (concat
(make-string
;; Insert white space up to next number.
(- (* symbol-width X-axis-label-spacing) 2)
? )
(number-to-string number)))
;; Insert remaining numbers.
(setq number (+ number X-axis-label-spacing))
(while (> number-of-X-tics 1)
(insert (X-axis-element number))
(setq number (+ number X-axis-label-spacing))
(setq number-of-X-tics (1- number-of-X-tics)))))
Finally, we need to write the print-X-axis that uses
print-X-axis-tic-line and print-X-axis-numbered-line.
The function must determine the local values of the variables used by both
print-X-axis-tic-line and print-X-axis-numbered-line, and then
it must call them. Also, it must print the carriage return that separates
the two lines.
The function consists of a varlist that specifies five local variables, and calls to each of the two line printing functions:
(defun print-X-axis (numbers-list)
"Print X axis labels to length of NUMBERS-LIST."
(let* ((leading-spaces
(make-string full-Y-label-width ? ))
;; symbol-width is provided by graph-body-print
(tic-width (* symbol-width X-axis-label-spacing))
(X-length (length numbers-list))
(X-tic
(concat
(make-string
;; Make a string of blanks.
(- (* symbol-width X-axis-label-spacing)
(length X-axis-tic-symbol))
? )
;; Concatenate blanks with tic symbol.
X-axis-tic-symbol))
(tic-number
(if (zerop (% X-length tic-width))
(/ X-length tic-width)
(1+ (/ X-length tic-width)))))
(print-X-axis-tic-line tic-number leading-spaces X-tic)
(insert "\n")
(print-X-axis-numbered-line tic-number leading-spaces)))
You can test print-X-axis:
X-axis-tic-symbol, X-axis-label-spacing,
print-X-axis-tic-line, as well as X-axis-element,
print-X-axis-numbered-line, and print-X-axis.
(progn
(let ((full-Y-label-width 5)
(symbol-width 1))
(print-X-axis
'(1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16))))
eval-expression).
yank).
Emacs will print the horizontal axis like this:
| | | | |
1 5 10 15 20
Previous: Similarities differences, Up: print-X-axis [Contents][Index]