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CONTENTS
CONTENTS
. . . . . . . . . . . . . . . . . . . . 110
. . . . . . . . . . . . . . . . . . . . . 110
. . . . . . . . . . . . . . . . . . . . . . . . 111
8.3.24 array dimension calculation
. . . . . . . . . . . . . . . . . 111
8.3.25 replacing pieces of a matrix
. . . . . . . . . . . . . . . . . 111
. . . . . . . . . . . . . . . . . . . . . . . . 112
. . . . . . . . . . . . . . . . . . . . . . 112
8.3.28 return is a function (still)
. . . . . . . . . . . . . . . . . . 113
. . . . . . . . . . . . . . . . . . . . . . . . 113
. . . . . . . . . . . . . . . . . . . . . . . 113
. . . . . . . . . . . . . . . . . . . . . . . . . 113
. . . . . . . . . . . . . . . . . . . . . . . 114
115
. . . . . . . . . . . . . . . . . . . . . . . 115
. . . . . . . . . . . . . . . . . . . . . . . . . . . . 116
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 116
. . . . . . . . . . . . . . . . . . . . . . . . 117
. . . . . . . . . . . . . . . . . . . . . . . . . . 117
Use a descriptive subject line
. . . . . . . . . . . . . . . . . . . . 118
. . . . . . . . . . . . . . . . . . . . . 118
. . . . . . . . . . . . . . . . . . . . . . . 120
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121
123
5
List of Figures
The giants by Sandro Botticelli.
. . . . . . . . . . . . . . . . . . .
14
The hypocrites by Sandro Botticelli.
. . . . . . . . . . . . . . . .
19
The panderers and seducers and the flatterers by Sandro Botticelli.
25
Stack of environments through time.
. . . . . . . . . . . . . . . .
32
The sowers of discord by Sandro Botticelli.
. . . . . . . . . . . .
36
The Simoniacs by Sandro Botticelli.
. . . . . . . . . . . . . . . .
41
The falsifiers: alchemists by Sandro Botticelli.
. . . . . . . . . . .
47
8.2
The treacherous to kin and the treacherous to country by Sandro
Botticelli.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
81
8.3
The treacherous to country and the treacherous to guests and
hosts by Sandro Botticelli.
. . . . . . . . . . . . . . . . . . . . . . 103
The thieves by Sandro Botticelli.
. . . . . . . . . . . . . . . . . . 116
The thieves by Sandro Botticelli.
. . . . . . . . . . . . . . . . . . 119
6
List of Tables
Time in seconds of methods to create a sequence.
. . . . . . . . .
12
. . . . . . . . . . . . . . . . .
20
The apply family of functions.
. . . . . . . . . . . . . . . . . . . .
24
. . . . . . . . . . . . . . . . . . . . . . . . . . . .
29
. . . . . . . . . . . . . . . . . . . . .
29
A few of the most important backslashed characters.
. . . . . . .
59
. . . . . . . . . . . . . . . . . . . .
61
7
Preface
Abstract:
If you are using R and you think you’re in hell, this is a map for
you.
wandered
through
To state the good I found there, I’ll also say what else I saw.
Having abandoned the true way, I fell into a deep sleep and awoke in a deep
dark wood. I set out to escape the wood, but my path was blocked by a lion.
As I fled to lower ground, a figure appeared before me. “Have mercy on me,
whatever you are,” I cried, “whether shade or living human.”
“Not a man, though once I was. My parents were from Lombardy. I was
born
sub Julio
and lived in Rome in an age of false and lying gods.”
“Are you Virgil, the fountainhead of such a volume?”
“I think it wise you follow me. I’ll lead you through an eternal place where
you shall hear despairing cries and see those ancient souls in pain as they grieve
their second death.”
After a journey, we arrived at an archway. Inscribed on it: “Through me
the way into the suffering city, through me the way among the lost.” Through
the archway we went.
Now sighing and wails resounded through the starless air, so that I too
began weeping. Unfamiliar tongues, horrendous accents, cries of rage—all of
these whirled in that dark and timeless air.
8
Circle 1
Falling into the Floating
Point Trap
Once we had crossed the Acheron, we arrived in the first Circle, home of the
virtuous pagans. These are people who live in ignorance of the Floating Point
Gods. These pagans expect
.1 == .3 / 3
to be true.
The virtuous pagans will also expect
seq(0, 1, by=.1) == .3
to have exactly one value that is true.
But
you
should not expect something like:
unique(c(.3, .4 - .1, .5 - .2, .6 - .3, .7 - .4))
to have length one.
I wrote my first program in the late stone age. The task was to program
the quadratic equation. Late stone age means the medium of expression was
punchcards. There is no backspace on a punchcard machine—once the holes
are there, there’s no filling them back in again. So a typo at the end of a line
means that you have to throw the card out and start the line all over again. A
procedure with which I became all too familiar.
Joy ensued at the end of the long ordeal of acquiring a pack of properly
punched cards. Short-lived joy. The next step was to put the stack of cards
into an in-basket monitored by the computer operator. Some hours later the
(large) paper output from the job would be in a pigeonhole. There was of course
an error in the program. After another struggle with the punchcard machine
(relatively brief this time), the card deck was back in the in-basket.
9