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I have some data (parts per million) where some of it is 1 or greater than one (but has an actual number.) However, some of the data simply lists "<1" ppm.

What is a good way to visualize this in a graph?

Should I pick an arbitrary decimal less than one, so that it can be shown on the graph? I feel setting it to zero would not be right either, as they went to the extent of listing it, so it must be significant.

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Is it a univariate plot? If so, just bin the data and toss it into the lowest bin.

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  • $\begingroup$ It is not. Currently I have it in histograms- but anything that shows as a <1 shows up as zero. (Excel Pivot Tables) $\endgroup$
    – mitchmitch24
    Commented Dec 5, 2017 at 16:51
  • $\begingroup$ A histogram is a univariate plot. A scatterplot is a bivariate plot. You could make a bar chart where all the <1's are in a bin. $\endgroup$
    – generic_user
    Commented Dec 5, 2017 at 17:30
  • $\begingroup$ Oh, I did not realize. And that makes sense. Thank you! $\endgroup$
    – mitchmitch24
    Commented Dec 5, 2017 at 18:29
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Usually a regulator will require that you use half of the "<" number.

the < means that the analysis measured ZERO of whatever was being measured but there is usually a lower limit of reading (a test might not be able to measure below say 5ppm so if they measure a Zero all they can really say is that the result must have been <5ppm because they couldn't measure anything. So what do you repot....5 ? or Zero? ....no you report 2.5ppm. halfway between the limit of reading and zero.

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