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...s with distances between them. How do I go between the pairs of items with distances to a two dimensional map. some sample data follows >From To Distance ItemA ItemA 0 ItemA ItemB 54 ItemA ItemC 43 ItemA ItemD 47 ItemA ItemE 44 ItemA ItemF 63 ItemA ItemG 35 ItemA ItemH 44 ItemA ItemI 43 ItemA ItemJ 79 ItemB ItemA 54 ItemB ItemB 0 ItemB ItemC 55 ItemB ItemD 61 ItemB ItemE 65 ItemB ItemF 72 ItemB ItemG 49 ItemB ItemH 57 ItemB ItemI 54 ItemB ItemJ 68 ItemC ItemA 43 ItemC ItemB 55 ItemC ItemC 0 ItemC ItemD 53 ItemC ItemE 63 ItemC ItemF 74 ItemC ItemG 48 ItemC ItemH 31 ItemC ItemI 59 ItemC ItemJ 5...

...eter item response model. The one parameter model is straightforward. A two-factor model requires a set of factor loadings multiplying a single random effect. For example, a logit model for the ith subject responding correctly to the jth item (j=1,..,J) is logit[p(ij)] = a1*item1(i) + ... + aJ * itemJ(i) + lambda1*item1(i)*u(i) + ... + lambdaJ*itemJ(i)*u(i) where the lambdas are factor loadings, with lambda1 fixed to 1.0 and item1-itemJ are dummy variables for the items. Thanks, Dan =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-= Daniel A. Powers, Ph.D. Department of Sociology University of T...