SQL Server R Services How to Resolve could not find function "%>%"

I'm using dplyr in my stored procedure. I'm passing in a dataset that's returned by querying responses based on a provided input parameter, StudyID. The goal is to return the results of dplyr from the R script back to the stored procedure. However, I receive the error in my question title.

My stored procedure is as follows:

ALTER PROCEDURE [dbo].[spCodeMeans]
-- Add the parameters for the stored procedure here
@StudyID int,
@StudyID_outer int
AS
BEGIN
-- SET NOCOUNT ON added to prevent extra result sets from
-- interfering with SELECT statements.
SET NOCOUNT ON;

-- Insert statements for procedure here

BEGIN TRY

        exec sp_execute_external_script
        @language = N'R',
        @script = N'
            # Summary Mean
            #
            # Calculates the mean of all independent variables in a table of data
            # grouped by \code{code}. Note that independent variables are
            # identified as all columns matching the following pattern: the letter
            # "c" followed by a one-or-more digit number.
            #
            # @param x Table to summarize
            # @importFrom rlang .data
            #
            # @return Summary table where each distinct \code{code} value is
            #   represented by one row with columns for the respective means of
            #   each independent variable.
            #install.packages("dplyr")

            code_mean <- function(x) {

              dplyr::group_by(x, .data$code) %>%
                dplyr::summarize_at(dplyr::vars(dplyr::matches("c\\d+")), mean)

            }

            cmresult <- code_mean(x = input_data_1)

            # Summary Standard Deviation
            #
            # Calculates the standard deviation of all independent variables in a
            # table of data grouped by \code{code}. Note that independent variables
            # are identified as all columns matching the following pattern: the
            # letter "c" followed by a one-or-more digit number.
            #
            # @param x Table to summarize
            # @importFrom rlang .data
            #
            # @return Summary table where each distinct \code{code} value is
            #   represented by one row with columns for the respective standard
            #   deviations of each independent variable.

            code_sd <- function(x) {

              dplyr::group_by(x, .data$code) %>%
                dplyr::summarize_at(dplyr::vars(dplyr::matches("c\\d+")), stats::sd)

            }

            sdresult <- code_sd(x = input_data_1)
        ',
    @input_data_1 = N'
        Select Responses = 
        c.StudyID, c.RespID, c.ProductNumber, c.ProductSequence, c.BottomScaleValue, 
        c.BottomScaleAnchor, c.TopScaleValue, c.TopScaleAnchor, c.StudyDate,
        c.DayOfWeek, c.A, c.B, c.C, c.D, c.E, c.F,
        c.DependentVarYN, c.VariableAttributeID, c.VarAttributeName, c.[1] as c1, 
        c.[2] as c2, c.[3] as c3, c.[4] as c4, c.[5] as c5, c.[6] as c6, c.[7] as c7, c.[8] as c8
        from ClosedStudyResponses c
        where DependentVarYN = 0
    ',
    @params = N'@StudyID int',
    @StudyID = @StudyID_outer
    --@output_data_1_name = N'dfcm',
    --@output_data_2_name = N'dfsd'

WITH RESULT SETS (
(cmsresult varchar(MAX)),
(sdresult varchar(MAX)))
END TRY

BEGIN CATCH
    THROW;
END CATCH
END

I call spCodeMeans per below:

DECLARE @out varchar(MAX), @out1 varchar(MAX);

EXEC    spCodeMeans
        @StudyID = 21,
        @StudyID_outer = 21

SELECT   @out, @out1;

GO

Error syntax:

Msg 39004, Level 16, State 20, Line 4
A 'R' script error occurred during execution of 'sp_execute_external_script' 
with HRESULT 0x80004004.
Msg 39019, Level 16, State 1, Line 4
An external script error occurred: 
Error in dplyr::group_by(x, .data$code) %>% 
dplyr::summarize_at(dplyr::vars(dplyr::matches("c\\d+")),  : 
could not find function "%>%"
Calls: source -> withVisible -> eval -> eval -> code_mean

Error in execution.  Check the output for more information.
Error in eval(ei, envir) : 
Error in execution.  Check the output for more information.
Calls: source -> withVisible -> eval -> eval -> .Call
Execution halted

How do I remedy the error such that the query results are passed into the R Script and both mean and standard deviation are returned?

Update Per comments, I added to the stored procedure so that it is now as follows:

    BEGIN TRY

        exec sp_execute_external_script
        @language = N'R',
        @script = N'
            # Summary Mean
            #
            # Calculates the mean of all independent variables in a table of data
            # grouped by \code{code}. Note that independent variables are
            # identified as all columns matching the following pattern: the letter
            # "c" followed by a one-or-more digit number.
            #
            # @param x Table to summarize
            # @importFrom rlang .data
            #
            # @return Summary table where each distinct \code{code} value is
            #   represented by one row with columns for the respective means of
            #   each independent variable.
            #install.packages("dplyr")

            code_mean <- function(x) {

              `%>%` = magrittr:: `%>%`
              dplyr::group_by(x, .data$code) %>%
                dplyr::summarize_at(dplyr::vars(dplyr::matches("c\\d+")), mean)

            }

            cmresult <- code_mean(x = input_data_1)

            # Summary Standard Deviation
            #
            # Calculates the standard deviation of all independent variables in a
            # table of data grouped by \code{code}. Note that independent variables
            # are identified as all columns matching the following pattern: the
            # letter "c" followed by a one-or-more digit number.
            #
            # @param x Table to summarize
            # @importFrom rlang .data
            #
            # @return Summary table where each distinct \code{code} value is
            #   represented by one row with columns for the respective standard
            #   deviations of each independent variable.

            code_sd <- function(x) {

              `%>%` = magrittr:: `%>%`
              dplyr::group_by(x, .data$code) %>%
                dplyr::summarize_at(dplyr::vars(dplyr::matches("c\\d+")), stats::sd)

            }

            sdresult <- code_sd(x = input_data_1)
        ',
    @input_data_1 = N'
        Select Responses = 
        c.StudyID, c.RespID, c.ProductNumber, c.ProductSequence, c.BottomScaleValue, 
        c.BottomScaleAnchor, c.TopScaleValue, c.TopScaleAnchor, c.StudyDate,
        c.DayOfWeek, c.A, c.B, c.C, c.D, c.E, c.F,
        c.DependentVarYN, c.VariableAttributeID, c.VarAttributeName, c.[1] as c1, 
        c.[2] as c2, c.[3] as c3, c.[4] as c4, c.[5] as c5, c.[6] as c6, c.[7] as c7, c.[8] as c8
        from ClosedStudyResponses c
        where DependentVarYN = 0
    ',
    @params = N'@StudyID int',
    @StudyID = @StudyID_outer
    --@output_data_1_name = N'dfcm',
    --@output_data_2_name = N'dfsd'

WITH RESULT SETS (
(cmsresult varchar(MAX)),
(sdresult varchar(MAX)))
END TRY

BEGIN CATCH
    THROW;
END CATCH
END

The original error is resolved and is replaced by the following:

Msg 39004, Level 16, State 20, Line 4
A 'R' script error occurred during execution of 'sp_execute_external_script' 
with HRESULT 0x80004004.
Msg 39019, Level 16, State 1, Line 4
An external script error occurred: 
Error in dplyr::group_by(x, .data$code) : object 'input_data_1' not found
Calls: source ... eval -> code_mean -> %>% -> eval -> eval -> <Anonymous>

Error in execution.  Check the output for more information.
Error in eval(ei, envir) : 
Error in execution.  Check the output for more information.
Calls: source -> withVisible -> eval -> eval -> .Call
Execution halted