Returns the help text for the specified topic formatted either as plain text, html or latex.

## Arguments

- topic
character, the topic for which to return the help text. See argument

`topic`

of function`help()`

for details.- format
character, either

`"text"`

,`"html"`

or`"latex"`

- package
character, the package for which to return the help text. This argument will be ignored if topic is specified. Package must be attached to the search list first, e.g. by calling

`library(package)`

.

## Examples

```
htm <- help2("sum", "html")
txt <- help2(topic = "sum", format = "text")
cat2(txt)
#> _S_u_m _o_f _V_e_c_t_o_r _E_l_e_m_e_n_t_s
#>
#> _D_e_s_c_r_i_p_t_i_o_n:
#>
#> ‘sum’ returns the sum of all the values present in its arguments.
#>
#> _U_s_a_g_e:
#>
#> sum(..., na.rm = FALSE)
#>
#> _A_r_g_u_m_e_n_t_s:
#>
#> ...: numeric or complex or logical vectors.
#>
#> na.rm: logical. Should missing values (including ‘NaN’) be removed?
#>
#> _D_e_t_a_i_l_s:
#>
#> This is a generic function: methods can be defined for it directly
#> or via the ‘Summary’ group generic. For this to work properly,
#> the arguments ‘...’ should be unnamed, and dispatch is on the
#> first argument.
#>
#> If ‘na.rm’ is ‘FALSE’ an ‘NA’ or ‘NaN’ value in any of the
#> arguments will cause a value of ‘NA’ or ‘NaN’ to be returned,
#> otherwise ‘NA’ and ‘NaN’ values are ignored.
#>
#> Logical true values are regarded as one, false values as zero.
#> For historical reasons, ‘NULL’ is accepted and treated as if it
#> were ‘integer(0)’.
#>
#> Loss of accuracy can occur when summing values of different signs:
#> this can even occur for sufficiently long integer inputs if the
#> partial sums would cause integer overflow. Where possible
#> extended-precision accumulators are used, typically well supported
#> with C99 and newer, but possibly platform-dependent.
#>
#> _V_a_l_u_e:
#>
#> The sum. If all of the ‘...’ arguments are of type integer or
#> logical, then the sum is ‘integer’ when possible and is ‘double’
#> otherwise. Integer overflow should no longer happen since R
#> version 3.5.0. For other argument types it is a length-one
#> numeric (‘double’) or complex vector.
#>
#> *NB:* the sum of an empty set is zero, by definition.
#>
#> _S_4 _m_e_t_h_o_d_s:
#>
#> This is part of the S4 ‘Summary’ group generic. Methods for it
#> must use the signature ‘x, ..., na.rm’.
#>
#> ‘plotmath’ for the use of ‘sum’ in plot annotation.
#>
#> _R_e_f_e_r_e_n_c_e_s:
#>
#> Becker, R. A., Chambers, J. M. and Wilks, A. R. (1988) _The New S
#> Language_. Wadsworth & Brooks/Cole.
#>
#> _S_e_e _A_l_s_o:
#>
#> ‘colSums’ for row and column sums.
#>
#> _E_x_a_m_p_l_e_s:
#>
#> ## Pass a vector to sum, and it will add the elements together.
#> sum(1:5)
#>
#> ## Pass several numbers to sum, and it also adds the elements.
#> sum(1, 2, 3, 4, 5)
#>
#> ## In fact, you can pass vectors into several arguments, and everything gets added.
#> sum(1:2, 3:5)
#>
#> ## If there are missing values, the sum is unknown, i.e., also missing, ....
#> sum(1:5, NA)
#> ## ... unless we exclude missing values explicitly:
#> sum(1:5, NA, na.rm = TRUE)
#>
```