REST API: Clarification of `riskFrequency` (RAF) in JSON responses

[ramiromagno]

The element riskFrequency appears in two places in the JSON responses:

• at the very top level as riskFrequency
• in loci > strongestRiskAlleles > riskFrequency

What is the difference between the two? Are they the same if the loci involved are single SNPs but different if it's a multi-SNP locus? In the web service, which one corresponds to the column RAF?

Example: Association 13731:

{
  "riskFrequency" : "0.18",
  "pvalueDescription" : "(AA)",
  "pvalueMantissa" : 3,
  "pvalueExponent" : -10,
  "multiSnpHaplotype" : true,
  "snpInteraction" : false,
  "snpType" : "novel",
  "standardError" : null,
  "range" : "[1.15-1.30]",
  "description" : null,
  "orPerCopyNum" : 1.22,
  "betaNum" : null,
  "betaUnit" : null,
  "betaDirection" : null,
  "loci" : [ {
    "haplotypeSnpCount" : 2,
    "description" : "2-SNP haplotype",
    "strongestRiskAlleles" : [ {
      "riskAlleleName" : "rs3818361-A",
      "riskFrequency" : null,
      "genomeWide" : false,
      "limitedList" : false,
      "_links" : {
        "snp" : {
          "href" : "https://www.ebi.ac.uk/gwas/rest/api/singleNucleotidePolymorphisms/rs3818361{?projection}",
          "templated" : true
        }
      }
    }, {
      "riskAlleleName" : "rs6656401-A",
      "riskFrequency" : null,
      "genomeWide" : false,
      "limitedList" : false,
      "_links" : {
        "snp" : {
          "href" : "https://www.ebi.ac.uk/gwas/rest/api/singleNucleotidePolymorphisms/rs6656401{?projection}",
          "templated" : true
        }
      }
    } ],
    "authorReportedGenes" : [ {
      "geneName" : "CR1",
      "entrezGeneIds" : [ {
        "entrezGeneId" : "1378"
      } ],
      "ensemblGeneIds" : [ {
        "ensemblGeneId" : "ENSG00000203710"
      } ]
    } ],
    "_links" : {
      "association" : {
        "href" : "https://www.ebi.ac.uk/gwas/rest/api/associations/13731{?projection}",
        "templated" : true
      }
    }
  } ],
  "lastMappingDate" : "2021-06-24T17:33:16.000+0000",
  "lastUpdateDate" : "2021-06-24T17:33:17.000+0000",
  "pvalue" : 3.0E-10,
  "_links" : {
    "self" : {
      "href" : "https://www.ebi.ac.uk/gwas/rest/api/associations/13731"
    },
    "association" : {
      "href" : "https://www.ebi.ac.uk/gwas/rest/api/associations/13731{?projection}",
      "templated" : true
    },
    "snps" : {
      "href" : "https://www.ebi.ac.uk/gwas/rest/api/associations/13731/snps"
    },
    "study" : {
      "href" : "https://www.ebi.ac.uk/gwas/rest/api/associations/13731/study"
    },
    "backgroundEfoTraits" : {
      "href" : "https://www.ebi.ac.uk/gwas/rest/api/associations/13731/backgroundEfoTraits"
    },
    "efoTraits" : {
      "href" : "https://www.ebi.ac.uk/gwas/rest/api/associations/13731/efoTraits"
    }
  }
}