Compile Errors with SPI

[kd8bxp]

This is the output of the debug screen on the Arduino IDE - (1.8.5) Archiving built core (caching) in: /tmp/arduino_cache_670098/core/core_RaspberryPi_piduino_bplus_SerialDestination_disabled,GDBDebug_disabled_dafffd944d7440de62a4aa1c8b0a2860.a sketch/sketch_mar24a.ino.cpp.o: In function setup': sketch_mar24a.ino.cpp:(.text+0x14): undefined reference to SPIClass::begin()' sketch_mar24a.ino.cpp:(.text+0x54): undefined reference to SPIClass::transfer(unsigned char)' sketch_mar24a.ino.cpp:(.text+0x60): undefined reference to SPIClass::transfer(unsigned char)' sketch_mar24a.ino.cpp:(.text+0x74): undefined reference to SPI' sketch/sketch_mar24a.ino.cpp.o: In function loop': sketch_mar24a.ino.cpp:(.text+0xac): undefined reference to SPIClass::transfer(unsigned char)' sketch_mar24a.ino.cpp:(.text+0xb8): undefined reference to SPIClass::transfer(unsigned char)' sketch_mar24a.ino.cpp:(.text+0xec): undefined reference to SPI' sketch/sketch_mar24a.ino.cpp.o: In function readout()': sketch_mar24a.ino.cpp:(.text+0x11c): undefined reference to SPIClass::transfer(unsigned char)' sketch_mar24a.ino.cpp:(.text+0x12c): undefined reference to SPIClass::transfer(unsigned char)' sketch_mar24a.ino.cpp:(.text+0x14c): undefined reference to `SPI' collect2: error: ld returned 1 exit status exit status 1 Error compiling for board RaspberryPI B+/2.

Not sure how to proceed.