Trouble plotting labels on lines

Q&A
1

Hello GMTers.
I’m having trouble plotting “quoted” lines in GMT6 modern-mode with the ‘plot’ command and the -Sq flag. I wonder what I’m getting wrong - or if I’ve encountered a bug. Any thoughts? Using GMT v6.0.0 via anaconda on OSX.

What I’m expecting:
The lines will plot with labels “A” and “B”, respectively. One label per line.

What I’m getting:
The lines are plotting with the label "N/A’ printed on both lines. One label per line.

Here’s my code, simplified:

#!/bin/bash
gmt begin test_line_labels png
    gmt basemap -R0/100/0/100 -B
    gmt plot -Sqn1+Lh <<EOF
> "A"
40 50
89 89
> -LB
10 10
80 30
EOF
gmt end

test_line_labels
test_line_labels1961×1904 43.5 KB

I’m basing my expectation on the doc page below. Trying both the “scan for an embedded -Llabel option” and the “use the first word following the segment” option.
http://gmt.soest.hawaii.edu/doc/latest/plot.html?highlight=plot#l
(viewed 2020-02-15)

+Lflag

    Sets the label text according to the specified flag:

    +Lh Take the label from the current segment header (first scan for an embedded -Llabel option, if not use the first word following the segment flag). 
For multiple-word labels, enclose entire label in double quotes.
2

Aaaannnnd I figured it out immediately after posting this question.
For anyone else encountering this issue, there needs to be a “colon” [:] to separate the label information (the +Lh) from the placement statement (n1). So,

gmt plot -Sqn1:+Lh

Although it’s subtle, this is stated in the docs

-Sq.  
quoted line, i.e., lines with annotations such as contours. Append [d|D|f|l|L|n|N|s|S|x|X]info[:labelinfo].  The required argument controls the placement of labels along the quoted lines. Choose among six controlling algorithms:

Perhaps the need for this colon could be more explcitly stated in the docs to avoid confusion. Thanks.

3

Thanks, I have added a line to alert users to the need for the colon.