If y-axis is amplitude and x-axis is frequency and you draw line then at each point of line the corresponding frequency has measured amplitude.
Meaning that you should have an array of frequencies [10Hz, 20Hz, 30Hz]
And for every item in frequency array you have measured (peak) amplitude [50dB,20dB,33dB] (whatever the displacement unit is).
Those make pairs. From chart perspective two-dimensional points. {x,y}
As you have an array of such points, you can draw line between them.
Such graph represents vibration spectrum.
I don't know anything about what the data is, but if it comes in as for single point, then may be something like that can be somehow represent the vibration spectrum.
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