tips and tricks

Date last run: 09Apr2021

Searching

R Debugging

trace(get_trends,quote(browser()),where=asNamespace("rtweet"))
rtweet::get_trends("amsterdam")
untrace(rtweet::get_trends)

as.list(body(rtweet:::get_trends_))
trace(rtweet:::get_trends_,
			quote(browser()),
			at=8,
			where=asNamespace("rtweet"))
rtweet::get_trends("amsterdam")
untrace(rtweet:::get_trends_)

browser() commands

From browser() function help info:

include code related to paths

Two methods to include code with highlighting. See that the two paths are different. In the first case the base directory is the note or post directory and in the second case the base directory is the project library.

`​``{r echo=T,eval=T,comment=''}
cat(readLines("../../R/update_HOQC.R",warn=F),sep="\n")
`​``


```{r include2,code=readLines("./R/update_HOQC.R",warn=F),eval=F}
```

insert graphics

Graphics created by an Rmd file post/2020-06-09-an-html-document-with-aside-s are placed in a subfolder of
static/post/2020-06-09-an-html-document-with-aside-s_files . We can use the same folder when we want to include other graphic files.

    `​``{R echo=F}
    getwd()
    #> [1] "D:/data/R/my_website_xmin/content/post"
    knitr::include_graphics('post/2020-06-09-an-html-document-with-aside-s_files/css.PNG',error=F)
    `​``
    
    in text we can use
    ![](/post/2020-06-09-an-html-document-with-aside-s_files/css.PNG)

Notice the difference in the (beginning of the) pathnames of the graphic file: for text (the markdown syntax) the pathname should start with a slash (/post/ ...) but in the R-code the slash should not be used (post/ ...). Also it is necessary to code error=F in the knitr::include_graphics call otherwise an error will occur because the path provided will not find the graphics file. In both cases the generated path in the html file will be ../../../../../post/ ...

insert footnotes

To insert a footnote use '[^fnptr]' ¹ where fnptr is an arbitrary but unique (in this document) identifier that references a text that is defined by including '[^fnptr]:' (note the ':') at the end of the document.

test only one file in active package

testthat:::test_package_dir(package = 'tabr', 
   test_path = './tests/testthat',
   filter = 'phrase',
   reporter=check_reporter())

include code chunks in text

In the section above we showed three consecutive backticks . This is not so easy as it seems because we generated the section (in fact the whole entry) with knitr where three such backticks are ‘eaten’ after being considered to be code block delimeters. See explanation. The second block used method 1 (adding empty string) in the explanation and for the first block the second (zero-width space) method was used.

include paired asteriks (*) in text

Paired asteriks are used to italicise a phrase. When you just want to display a phrase within asteriks e.g. *italics* use the html escape code *  .

include non-breaking space in text

Use the html-code    .

include session_info chunk

Use

`​``{r child='../../local_files/session_info.Rmd'} 
`​`` 

to include the standard session_info chunk.

solution for empty line before last entry in list

After hugo version 0.57 I noticed that a list immediately followed by a code block forces an empty line between the list and its last entry. This can be solved by inserting a new line (so we see an empty line) and a comment like <!-- inserted to avoid incorrect list ending -->
after the last entry.

documentation with Roxygen2

Since version 2.7 there are several website with improved information about Roxygen2:

• The roxygen2 7.0.0 announcement
• The roxygen2 website
• Links!

activate Git in RStudio

When an RStudio project is created without Git, there is no invisible indication of Git functionality. Select/open the terminal pane and make sure that the active folder is the main folder of the project. Then type git init in the terminal pane. After closing and reopening the project in RStudio the Git pane will show.

dates and times

The anytime package interprets characters in local time (i.e. ‘Europe/Berlin’ here) when asUTC == F and otherwise as a UTC time. When the time is given as a character it will be represented in the timezone specified with the tz argument and when none is specified in the local timezone. However when the time is a POSIX object no conversion to a timezone will take place.

HOQCutil::silent_library(anytime)
nowp = Sys.time() ; str(nowp) 
#>  POSIXct[1:1], format: "2021-04-09 10:00:28"
x=anytime(nowp,tz="America/New_York",asUTC=F) ;str(x) # will not convert POSIX !
#>  POSIXct[1:1], format: "2021-04-09 10:00:28"
nowc = as.character(nowp) ; str(nowc) # no longer POSIX but character only
#>  chr "2021-04-09 10:00:28"
x=anytime(nowc,tz="America/New_York",asUTC=F) ;str(x) # will convert to New York timezone
#>  POSIXct[1:1], format: "2021-04-09 04:00:28"
x=anytime(nowc,tz="America/New_York",asUTC=F) ;str(x+60*60*24) # New York time over a day
#>  POSIXct[1:1], format: "2021-04-10 04:00:28"

x=anytime(nowc,tz="Europe/Amsterdam",asUTC=T) ;str(x) # interpreted as UTC time and represented in Amsterdam time
#>  POSIXct[1:1], format: "2021-04-09 12:00:28"
x=anytime(nowc,asUTC=T) ;str(x) # interpreted as UTC time and represented in local (= Amsterdam) time
#>  POSIXct[1:1], format: "2021-04-09 12:00:28"
x=anytime(nowc,tz="America/New_York",asUTC=T) ;str(x) # interpreted as UTC time and represented in New York time
#>  POSIXct[1:1], format: "2021-04-09 06:00:28"
x=anytime(nowc,tz="America/New_York",asUTC=T) ;str(x+60*60*24) # New York time over a day
#>  POSIXct[1:1], format: "2021-04-10 06:00:28"

The website TWiki.org Service: Date and Time Gateway - Timezone Selector has an overview of possible timezone codes.

keyboard shortcuts

From Handboek Internetresearch & datajournalistiek and 47 Keyboard Shortcuts That Work in All Web Browsers

Google (Groups) Common search techniques

From Common search techniques and Handboek Internetresearch & datajournalistiek :

Footnotes: