weightSMART
SMART Weightings
Weight a term-document matrix according to a combination of weights specified in SMART notation.
Usage
weightSMART(m, spec = "nnn", control = list())
Arguments
- m
- A
TermDocumentMatrix
in term frequency format. - spec
- a character string consisting of three characters. The first letter specifies a term frequency schema, the second a document frequency schema, and the third a normalization schema. See Details for available built-in schemata.
- control
- a list of control parameters. See Details.
Details
Formally this function is of class WeightingFunction
with the
additional attributes Name
and Acronym
.
The first letter of spec
specifies a weighting schema for term
frequencies of m
:
- "n"
- (natural) $\mathit{tf}_{i,j}$ counts the number of occurrences
$n_{i,j}$ of a term $t_i$ in a document $d_j$. The
input term-document matrix
m
is assumed to be in this standard term frequency format already.
The second letter of spec
specifies a weighting schema of
document frequencies for m
:
- "n"
- (no) is defined as 1.
The third letter of spec
specifies a schema for normalization
of m
:
- "n"
- (none) is defined as 1.
slope
and pivot
must be set
via named tags in the control
list.
alpha
in the control
list.
The final result is defined by multiplication of the chosen term frequency component with the chosen document frequency component with the chosen normalization component.
Value
-
The weighted matrix.
References
Christopher D. Manning and Prabhakar Raghavan and Hinrich Schütze (2008). Introduction to Information Retrieval. Cambridge University Press, ISBN 0521865719.
Examples
data("crude")
TermDocumentMatrix(crude,
control = list(removePunctuation = TRUE,
stopwords = TRUE,
weighting = function(x)
weightSMART(x, spec = "ntc")))