7. A computer-implemented information retrieval method-comprising: receiving, via a processor, a search query from a user, wherein the search query comprises a plurality of keywords; calculating, via the processor, a relevance to a plurality of documents, wherein the relevance is based on the plurality of keywords and an influence set for each keyword, wherein the relevance is calculated based on a mathematical product of: a number of keywords in a search query in a document; a frequency of a keyword appearing in the document; a proportion of documents containing the keyword; a weight of the keyword; and a weight for a date indicative of when a search index was created; displaying on the display device, via the processor, documents in the an order of relevance; displaying on the display device, via the processor, the influence set for each keyword; receiving, via the processor, changes to the displayed influence by the user; and recalculating, via the processor, the relevance on the basis of a change to the influence and displaying on the display device documents in the order of relevance.
7. A computer-implemented information retrieval method-comprising: receiving, via a processor, a search query from a user, wherein the search query comprises a plurality of keywords; calculating, via the processor, a relevance to a plurality of documents, wherein the relevance is based on the plurality of keywords and an influence set for each keyword, wherein the relevance is calculated based on a mathematical product of: a number of keywords in a search query in a document; a frequency of a keyword appearing in the document; a proportion of documents containing the keyword; a weight of the keyword; and a weight for a date indicative of when a search index was created; displaying on the display device, via the processor, documents in the an order of relevance; displaying on the display device, via the processor, the influence set for each keyword; receiving, via the processor, changes to the displayed influence by the user; and recalculating, via the processor, the relevance on the basis of a change to the influence and displaying on the display device documents in the order of relevance. 11. The information retrieval method of claim 7 , further comprising displaying the influence of each keyword linearly, and changing the influence of each keyword in accordance with movement of a boundary of each linearly displayed keyword.