Need Help for a query

Hello,

            I am
using this pqxx library for postgresql to run programs.The following is
the query which i gave to store the data,here data.speed,data.heading
are float values and data.ttime is timestamp .If i try to run this
statement I end up with an error below this query.Please help me to
solve this problem.

 result R1(T1.exec("insert into saveodtdata values( "+data.speed+" ,  "+data.heading+" , '" +data.ttime+" ' )" ));

 invalid operands of types `const char[33]' and `float' to binary `operator+'make: *** [main2.o] Error 1

Thank You,

Avinash.