R markdown error

[Gg_R]

Hi, can someone tell me what does this error message mean? I am using the survey package to apply the svydesign function.

Code: 

ihisDesign1 <- svydesign(id=~PSU, strata=~STRATA, weights=~SAMPWEIGHT, nest=TRUE, data= ihisFinal)

Error Message after selecting 'Knit HTML' in R Studio: 

Error in eval(expr, envir, enclos) : could not find function "svydesign"

Calls: <Anonymous> ... handle -> withCallingHandlers -> withVisible -> eval -> eval

Execution halted

[Gg_R]

ok, I figured it out. I need to add the following code before applying survey design. 

require(survey)

[Yihui Xie]

I hate repeating it, but it is library():
http://yihui.name/en/2014/07/library-vs-require/

Regards,
Yihui
--
Yihui Xie <xiey...@gmail.com>
Web: http://yihui.name

[Rafael Sierra]

I'm getting this same error in markdown but with any operation that requires to evaluate a variable in the workspace. Does anybody know why that would be happening?