Analyse des Correspondances Multiples Parcimonieuse

International audienceMultiple Correspondence Analysis (MCA) is the method of choicefor themultivariate analysis of categorical data. In MCA each qualitative variable is representedby a group of binary variables (with a coding scheme called “complete disjunctive coding”)and each binary variable has a weight inversely proportional to its frequency. The datamatrix concatenates all these binary variables, and once normalized and centered thisdata matrix is analyzed with a generalized singular value decomposition (GSVD) thatincorporates the variable weights as constraints (or “metric”). The GSVD is, of course,based on the plain SVD and so MCA can be sparsified by extending algorithms designedto sparsify the SVD. To do so requires two additional features: to include weights andto be able to sparsify entire groups of variables at once. Another important feature ofsuch a sparsification should be to preserve the orthogonality of the components, Here, weintegrate all these constraints by using an exact projection scheme onto the intersectionof subspaces (i.e., balls) where each ball represents a specific type of constraints. Weillustrate our procedure with the data from a questionnaire survey on the perception ofcheese in two French cities

Analyse des Correspondances Multiples Parcimonieuse

International audienceMultiple Correspondence Analysis (MCA) is the method of choicefor themultivariate analysis of categorical data. In MCA each qualitative variable is representedby a group of binary variables (with a coding scheme called “complete disjunctive coding”)and each binary variable has a weight inversely proportional to its frequency. The datamatrix concatenates all these binary variables, and once normalized and centered thisdata matrix is analyzed with a generalized singular value decomposition (GSVD) thatincorporates the variable weights as constraints (or “metric”). The GSVD is, of course,based on the plain SVD and so MCA can be sparsified by extending algorithms designedto sparsify the SVD. To do so requires two additional features: to include weights andto be able to sparsify entire groups of variables at once. Another important feature ofsuch a sparsification should be to preserve the orthogonality of the components, Here, weintegrate all these constraints by using an exact projection scheme onto the intersectionof subspaces (i.e., balls) where each ball represents a specific type of constraints. Weillustrate our procedure with the data from a questionnaire survey on the perception ofcheese in two French cities

Time to Agree

This article explores the impact of time pressure on negotiation processes in territorial conflicts in the post-cold war era. While it is often argued that time pressure can help generate positive momentum in peace negotiations and help break deadlocks, extensive literature also suggests that perceived time shortage can have a negative impact on the cognitive processes involved in complex, intercultural negotiations. The analysis explores these hypotheses through a comparison of sixty-eight episodes of negotiation using fuzzy-set logic, a form of qualitative comparative analysis (QCA). The conclusions confirm that time pressure can, in certain circumstances, be associated with broad agreements but also that only low levels of time pressure or its absence are associated with durable settlements. The analysis also suggests that the negative effect of time pressure on negotiations is particularly relevant in the presence of complex decision making and when a broad range of debated issues is at stake