Demonstration of interaction model

interObj.R

df <-
structure(list(muc6 = c(0.65991920232772827, 12.234284400939941,
7.5393352508544922, 13.921844482421875, 4.8508410453796387, 0,
6.7801151275634766, 5.5127406120300293, 1.030299186706543, 3.5845346450805664,
0.98191821575164795, 0, 0, 1.052558422088623, 0, 0, 2.5294754505157471,
0.59700602293014526, 0, 0, 7.0485143661499023, 0, 0, 0, 1.1008850336074829,
5.777961254119873, 6.1289887428283691, 0, 4.9814505577087402,
0, 5.4703717231750488, 8.0720577239990234, 0), tumortype = c("Carcinoma",
"sarcoma", "Carcinoma", "Carcinoma", "sarcoma", "sarcoma", "Carcinoma",
"Carcinoma", "sarcoma", "sarcoma", "Carcinoma", "Carcinoma",
"sarcoma", "Carcinoma", "sarcoma", "Carcinoma", "sarcoma", "Carcinoma",
"sarcoma", "sarcoma", "sarcoma", "sarcoma", "Carcinoma", "sarcoma",
"sarcoma", "sarcoma", "Carcinoma", "sarcoma", "sarcoma", "sarcoma",
"sarcoma", "Carcinoma", "Carcinoma"), auc = c(0.60560000000000003,
0.18579999999999999, 0.36320000000000002, 0.087099999999999997,
0.40010000000000001, 0.62670000000000003, 0.90359999999999996,
0.086199999999999999, 0.99039999999999995, 0.31869999999999998,
0.4466, 0.44219999999999998, 1.2351000000000001, 0.9194, 0.58389999999999997,
0.38469999999999999, 0.45200000000000001, 0.71909999999999996,
0.61950000000000005, 0.93520000000000003, 0.1203, 0.35549999999999998,
0.39750000000000002, 0.66159999999999997, 0.53410000000000002,
0.13039999999999999, 0.48570000000000002, 0.75180000000000002,
0.23100000000000001, 0.75849999999999995, 0.19359999999999999,
0.23250000000000001, 0.29330000000000001)), row.names = c("V1",
"V2", "V3", "V4", "V6", "V7", "V8", "V9", "V10", "V11", "V13",
"V14", "V15", "V16", "V17", "V18", "V20", "V21", "V22", "V23",
"V24", "V25", "V26", "V27", "V28", "V29", "V30", "V33", "V34",
"V35", "V36", "V37", "V38"), class = "data.frame", na.action = structure(c(V5 = 5L,
V12 = 12L, V19 = 19L, V31 = 31L, V32 = 32L), class = "omit"))