r - Using both in_header and header_includes in Rmarkdown and knitr -

i have long .txt file contains packages , settings want used in rmarkdown file. want add statements header, based on output of r calculations. in particular case want add titlegraphic located in directory, this:

working directory |--- reports |----| my_report.rmd |--- www |----| image.png 

so header of rmarkdown file like:

output:   beamer_presentation:     keep_tex: true     includes:       in_header: header.txt header-includes: - \titlegraphic{\includegraphics[width=0.3\paperwidth]{`r paste0("dirname(getwd()),"image.png")`}} 

if 1 of statements included (in_header or header-includes), work fine. when use them both, the content of header-includes seems overwritten. example given in files below, upon inspecting resulting .tex file, find \usepackage{fancyhdr} in header, there no mention of `\titlegraphic' expression.

---

header.txt

\usepackage{fancyhdr} 

---

example.rmd

title: example 1 output:   beamer_presentation:     keep_tex: true     includes:       in_header: header.txt header-includes:       \titlegraphic{\includegraphics[width=0.3\paperwidth]{`r paste0("just_an_example_","logo.png")`}} ---  ### test 

i think put in header-includes:

--- title: example 1 output:   beamer_presentation:     keep_tex: true header-includes:   - \titlegraphic{\includegraphics[width=0.3\paperwidth]{`r paste0("just_an_example_","logo.png")`}}   - \input{header.txt} --- 

does work? can't reproduce example.