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Figure 3
The use of the Pearson (r) and Spearman (ρ) correlation coefficients. (a) r = 0.93; ρ = 0.68. The high value of r arises from the perfect match of the two biggest peaks around 12 and 25° in 2θ, but the much lower Spearman coefficient acts as a warning that there are unmatched regions in the two patterns. (b) r = 0.79; ρ = 0.90. The lower value of r is due to peak offsets around 6° and the peak at 29°. Visual inspection of the two patterns indicates a high degree of similarity however, which is reflected in the Spearman coefficient of 0.9. (c) r = 0.66; ρ = 0.22. The value of r reflects the peak at 6°; the low value of ρ indicates a poor match in other regions.

Journal logoJOURNAL OF
APPLIED
CRYSTALLOGRAPHY
ISSN: 1600-5767
Volume 37| Part 2| March 2004| Pages 231-242
doi:10.1107/S002188980400038X
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