APEX line survey of R Dor (black). Labels show the carrier molecule of the indicated emission. Red labels indicate tentative or unidentified detections. Purple labels (Im(...)) pertain to emission contaminating the signal from the image sideband (see Sect. 2). For visibility, some parts of the survey were rescaled to fit the vertical scale. The colour coding of the spectrum corresponds to the following scale factors: (black) 1; (green) 1/5; (blue) 1/25; (red) 1/125. Notethe gap in the range 321.5–328.0 GHz. We also show the IRAM 30 m survey of IK Tau (orange; Velilla Prieto et al. 2017) for direct comparison of the two data sets. The IK Tau spectrum has been scaled according to the description in Appendix C.