Strange error calling an R script

Hello Expert,

I'm studying on SAP HANA R Integration, and following the examples I wrote an R script by my self, which is not working:

DROP TABLE PR_TEST_R_ROW_TABLE;
CREATE ROW TABLE PR_TEST_R_ROW_TABLE ( result0 varchar(5000) ) ;
DROP PROCEDURE PR_TEST_R_2;
CREATE PROCEDURE PR_TEST_R_2( OUT result0 "PR_TEST_R_ROW_TABLE")
LANGUAGE RLANG AS
BEGIN  result0 <- data.frame("R");
END;
CALL PR_TEST_R_2(?);

when I CALL my procedure the error is:

Could not execute 'CALL PR_TEST_R_2(?)' in 208 ms 323 µs .

SAP DBTech JDBC: [2048]: column store error: search table error:  [34086] Convert data error: Convert Data from R to NewDB failed.;Column 'RESULT0' not computed from R.

So I try to fix:

DROP TABLE PR_TEST_R_ROW_TABLE;
CREATE ROW TABLE PR_TEST_R_ROW_TABLE ( result0 varchar(5000) ) ;
DROP PROCEDURE PR_TEST_R_2;
CREATE PROCEDURE PR_TEST_R_2( OUT result0 "PR_TEST_R_ROW_TABLE")
LANGUAGE RLANG AS
BEGIN  RESULT0 <- data.frame("R");
END;
CALL PR_TEST_R_2(?);

but now the error is:

Could not execute 'CALL PR_TEST_R_2(?)' in 250 ms 911 µs .

SAP DBTech JDBC: [2048]: column store error: search table error:  [34084] Receive error: get result error.;Error: object 'result0' not found

stack trace:

No traceback available

I took a read of R Output Column Store Error but still cannot make it working, which is confusing me A LOT.

Any help is really appreciated,

thanks in advance

Pierre