Column widths not aligned with table data in pander tables sent from R with sendmailr

Question

I'm working with the 'pander' and 'sendmailr' packages to send a small data frame in the body of an email, rather than as an attachment. I'd like to send it from and to a gmail account.

I'm close, but the column headers won't align with the columns themselves in the email body the way they do in Rstudio for example- basically the column headers are too wide to line up with the data columns below them.

It seems the problem is the way the dashes and whitespaces are compressed in various email clients (I tried this in gmail, yahoo and hotmail through the web and through the email client that ships with OS X Mavericks). I was able to remedy the problem in my OS X email client by going to 'preferences' and checking the box labeled 'use fixed-width font for plain-text messages' but I'd like it to work on multiple devices, with multiple clients, etc for many of my coworkers so I'm wondering if there's a way that doesn't involve global email settings.

Here is the code to reproduce the problem:

library(sendmailR) # for emails from R
library(pander) # for table-formatting that does not require HTML

results <- head(iris)
pander(results) # widths look great so far...
a = pandoc.table.return(results)
strsplit(a, "\n") # widths still look great...

panderOptions('table.split.table', Inf) # show all columns on same line

msg_content <- mime_part(
  pandoc.table.return(results, style = "multiline")
)

# I'm using my own gmail address for email_from and email_to
sendmail(from = email_from,
         to = email_to,
         subject = "test",
         msg = msg_content
)

… and the email received has the problem described above.

Next you can see an image which illustrates the problem:

Described problem

You can leave the image link and we add it for you. – Werner Dec 30 '14 at 01:10 — Werner, Dec 30 '14 at 01:10
Thanks @Werner! http://i.stack.imgur.com/pM98F.png – Eric Dec 30 '14 at 01:21 — Eric, Dec 30 '14 at 01:21

score 6 · Accepted Answer · edited Jul 07 '16 at 09:50

The problem with plain text e-mails and using markdown tables is that the e-mail client usually displays the text with a non-fixed font, and you have to use custom settings in all your e-mail client to override that (like you did with your OS X e-mail client). On the other hand, that's why HTML mails are trending :)

So let's create a HTML mail and include the markdown table in a pre block:

msg_content <- mime_part(paste('<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0
Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
  <meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
  <meta name="viewport" content="width=device-width, initial-scale=1.0"/>
</head>
<body><pre>', paste(pander.return(results, style = "multiline"), collapse = '\n'), '</pre></body>
</html>'))

Due to a bug in sendmailR, we have to override the Content-type to HTML:

msg_content[["headers"]][["Content-Type"]] <- "text/html"

And now it's ready to be sent via the comment you used in your example, resulting in:

Pander markdown table in HTML mail

The table should look similarly fine in any other HTML-capable e-mail client. Please note that this way you could also use HTML tables instead of markdown if that would fit your needs better.

Column widths not aligned with table data in pander tables sent from R with sendmailr

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