formatci(ci, style=c("+/-", "parentheses"), model, digits=NULL)getOption("digits") is used.ci is given, the result is a character string with the
estimate and its uncertainty, in plus/minus or parenthetic notation.
If model is given, the result is a 1-column matrix holding
character strings, with row names corresponding to the parameters of
the model.model is given, then ci is ignored, and a
confidence interval is calculated using confint with
level set to 0.6914619. This level corresponds to a
range of plus or minus one standard deviation, for the t distribution
and a large number of degrees of freedom (since qt(0.6914619,
100000) is 0.5). If model is missing, ci must be provided. If it
contains 3 elements, then first and third elements are taken as the
range of the confidence interval (which by convention should use the
level stated in the previous paragraph), and the second element
is taken as the central value. Alternatively, if ci has 2
elements, they are taken to be bounds of the confidence interval and
their mean is taken to be the central value.
In the +/- notation, e.g. $a \pm b$ means that the
true value lies between $a-b$ and $a+b$ with a high
degree of certainty. Mills et al. (1993, section 4.1 on page 83)
suggest that $b$ should be set equal to 2 times the standard
uncertainty or standard deviation. JCGM (2008, section 7.2.2 on pages
25 and 26), however, suggest that $b$ should be set to the
standard uncertainty, while also recommending that the $\pm$
notation be avoided altogether.
The parentheses notation is often called the compact notation.
In it, the digits in parenthese indicate the uncertainty in the
corresponding digits to their left, e.g. 12.34(3) means that the last
digit (4) has an uncertainty of 3. However, as with the
$\pm$ notation, different authorities offer different advice
on defining this uncertainty; Mills et al. (1993, section 4.1 on page
83) provide an example in which the parenthetic notation has the same
value as the $\pm$ notation, while JCM (2008, section 7.2.2
on pages 25 and 26) suggest halving the number put in parentheses.
The foramtci function is based on the JCM (2008) notation,
i.e. formatci(ci=c(8,12), style="+/-") yields "10+-2",
and formatci(ci=c(8,12), style="parentheses") yields
"10(2)".
Note: if the confidence range exceeds the value, the
parentheses format reverts to +/- format.
+- sign and in parentheses.)
I. Mills, T. Cvitas, K. Homann, N. Kallay, and K. Kuchitsu, 1993.
Quantities, Units and Symbols in Physical Chemistry, published
Blackwell Science for the International Union of Pure and Applied
Chemistry. [+- sign is to be halved if put in
parentheses.)x <- seq(0, 1, length.out=300)
y <- rnorm(n=300, mean=10, sd=1) * x
m <- lm(y~x)
print(formatci(model=m))Run the code above in your browser using DataLab