sexuality is an integrant and essential part of quality of life ( qol ) , and patient affected 
 by neurological disability , including stroke , should also be investigated and treated for 
 sexual disorders1 . sexual dysfunction is 
 common after stroke , but is frequently not addressed by healthcare providers2 . the latter is defined as a decline in libido in both genders , erectile 
 dysfunction and poor ejaculation in men and diminished lubrication and orgasm in women3 , 4 . post - stroke patients reported a marked decline in all the measured sexual functions , ie , 
 libido , coital frequency , erectile and orgastic ability , and vaginal lubrication , as well as 
 in their sexual satisfaction . the spouses also reported a significant decline in their 
 libido , sexual activity , and sexual satisfaction as a consequence of stroke5 . sexual dysfunctions after stroke reported 
 to be due to multiple etiologies , including both physical and psychosocial causes1 , 2 . sexual function relies on a complex network of peripheral and central pathways involving 
 the participation of autonomic and somatic nerves and the integration of numerous spinal and 
 supraspinal sites in the central nervous system , with the hypothalamic and limbic regions 
 playing a pivotal role6 , 7 . many studies have shown significant relationships between symptoms of depression and 
 functional outcome in patients from 3 months to 2  years after stroke . also , reduced quality 
 of life after stroke appears to be related not only to the physical disability but also to 
 psychologic factors8,9,10 . depression and fear of a 
 recurrent stroke are examples of psychological factors influencing sexual function and , in 
 particular , sexual desire3 . the role of 
 psychological factors in poststroke sexual dysfunctions ( sd ) is further confirmed by the 
 observation that sexual disorders are reported not only by the patients , but also by their 
 spouses or partners8 , 11 , 12 . nevertheless , most of 
 the patients received little information about sexuality following stroke on sexual behavior 
 and attitudes of the stroke patients spouses , although they are very important in terms of 
 stroke survivors well - being . the decreased sexual activities of the stroke patients in korea mainly result from 
 psychological burden and physical disability caused by a disorder , but most of them tend to 
 avoid consultation with experts13 . additionally , avoiding sexual intercourse and conversation is another important factor of 
 decreasing sexual life due to a concern about aggravating a spouse s condition14 . random forest is a bagging algorithm which reduces variance of a large number of  complex models with low bias15 . while boosting , 
 which uses a set of week classifiers and combine them to derive a strong classifier , reduces 
 bias of a large number of  small  models with low variance16 . we compared the result of some machine learning algorithms , among 
 them random forest and boosting algorithm are the best for our purpose . many studies on changed psychological and physical health regarding rehabilitation after 
 stroke have been conducted , but there are not enough comparative studies on the general 
 characteristics of the patients and sexual index . the purpose of this study was to examine 
 patient preferences for counseling related to sexuality of post - stroke patients in korea by 
 using the random forest , boosting algorithm and manova . studies about stroke patients 
 sexual life which were unofficially discussed could be an important factor to improve the 
 quality of patients life and family life including a spouse as well . the survey was conducted by 147 patients who were diagnosed with stroke from university 
 hospitals located in seoul / gyeonggi , south korea . the survey procedure was sufficiently 
 explained beforehand to the subjects who voluntarily participated by signing the survey 
 consent form . we firstly revised and used brief sexual functioning questionnaire for men ( bsfq ) and brief 
 index of sexual functioning for woman ( bisf - w ) . the revised bsfq , bisf - w are used to 
 diagnose a disorder of sexual behavior and function , according to the objective of this 
 study17 , 18 . the revised questionnaire was then reviewed by an expert group 
 consisting of three professors in the department of physical therapy to examine content 
 validity and suitability of the questions . the questionnaire was composed of 27 questions 
 such as 8 independent variables related general characteristics of the patients , 7 dependent 
 variables in conjunction with sexual intercourse and changed muscle tone , 6 questions 
 regarding a changed sexual function , and 6 questions about a changed motor and a sensory 
 function after stroke ( table 1table 1.classification of group and definition 
 for each variablesgroupvariablesdefinitiongroupvariablesdefinitionindependent1duration of illnessdependent 315changes of 
 muscle tone after strokedependent 12communication about sexual activities16balance ability after stroke3necessity of study about sexual 
 activities17fine movement 
 after stroke4have a sex partner18changes of tactile sense after stroke5try to sexual intercourse after stroke19changes of smell sense after 
 stroke6frequency 
 of sexual intercourse / month20changes of taste sense after stroke7changes of muscle tone during sexual 
 intercourseindependent21gender8level of 
 muscle tone during sexual intercourse22agedependent 29changes of frequency of sexual intercourse after stroke23weight10frequency of kissing and 
 romantic touching after stroke24marriage11thinking about sex with interest or desire after 
 stroke25occupation12ability to become sexually aroused after stroke26education level13overall level of sexual 
 satisfaction after stroke27income level / month14obstacles during sexual intercoursedependent 1 : sexual intercourse and changed 
 muscle tone ; dependent 2 : changed sexual function ; dependent 3 : changed motor & 
 sensory function ) . the alpha value of cronbach was 
 0.688 which was used to indicate internal consistency of the dependent variables . data for 
 this study had been collected for 98 days : feasibility study for 8 days and main survey 90 
 days . a physical therapist at the hospital fully explained the objectives and procedures of 
 this study to the patients , and the questionnaires were filled by voluntary patients . total 
 156 questionnaires out of 200 were collected , and 147 questionnaires except 9 unsuitable 
 questionnaires were used for final analysis . dependent 1 : sexual intercourse and changed 
 muscle tone ; dependent 2 : changed sexual function ; dependent 3 : changed motor & 
 sensory function the collected questionnaires were analyzed by r version 3.3.1 . to figure out an 
 interrelationship between the general characteristics of the patients and the variables of 
 the sexual function , random forest , boosting algorithm and manova the general characteristics of 147 subjects are age , duration of illness , weight , gender , 
 marital status , education level , income level and occupation . the mean age of our study 
 population ( 97 men ; 65.99% and 50 women ; 34.00% ) was 53.56  years . the forty - six patients ( 31.30% ) have more than 1  year but 
 no longer than 3  years of a duration of illness , and it is examined the mean duration of 
 illness is 3.18  years . for the weight factor , the most number of the patients are fifty - four 
 ( 36.73% ) whose weight is between 60  kg and 70  kg , and its mean is 67.05  kg . for the martial 
 status factor , one hundred thirty - seven patients ( 93.20% ) the factor of education level , sixty - seven patients 
 ( 45.58% ) are graduated in high school . for the income level factor , fifty - six ( 38.10% ) of 
 patient s income is over 3 million won per month . in occupation factor , self - employed 
 patients are twenty - eight ( 19.05% ) , company employee twenty - two ( 14.97% ) , housewife eighteen 
 ( 12.24% ) . the random forest is the best method to find variable importance , we applied this method 
 for each variable group , in variable group 1 , var1 is the most important , and then var22 , 
 var23 , var26 , var27 , var25 , var21 and var 24 respectively . the most important variable in 
 variable group 2 is var22 , and then var26 , var23 , var25 , var1 , var27 , var21 and var 24 . finally , for variable group 3 , var1 has the most important percentage , and we have the order 
 var26 , var23 , var27 , var22 , var25 , var21 and var 24 among the rest of variables ( table 2table 
 2.interrelationship between the general characteristics of the 
 patients and the variables of the sexual functionindependent 
 variablesdependent 
 variablesgroup 1group 2group 
 3%incmse%incmse%incmse130.6***19.3***29.5**2115.5**14.419.52226.5***28.7***24.72325.2***25.2 * 26.7**2410.7***10.1 * 4.82519.619.6**22.12623.3***25.4***27.32723.1**19.3 * 25.5%incmse : % increase in mse ( mean 
 squared error)variable importance in random forest*p0.05 ; * * p0.01 ; 
 * * * p0.001 ) . % incmse : % increase in mse ( mean 
 squared error ) variable importance in random forest * p0.05 ; * * p0.01 ; 
 * * * p0.001 the result of variable importance in boosting algorithm is somehow the same as that of 
 random forest . the purpose of this study was to examine patient preferences for counseling related to 
 sexuality of post - stroke patients in korea by using the random forest , boosting algorithm 
 and manova . random forest is an excellent method to determine variable importance , as it fits a number 
 of decision tree classifiers on various sub - samples of the dataset . it uses averaging to 
 improve the predictive accuracy and control over - fitting , so there is no need for 
 cross - validation to get better ( or unbiased ) estimation , since according what we said it is 
 already done internally . however , it is difficult to interpret the result with multiple 
 outcome variables in random forest , for this purpose using multivariate tree boosting that 
 is a method for non - parametric regression is useful . in this study we are extending these 
 three methods along with linear regression for one group of independent variable and three 
 different groups of dependent variables to analyze the dataset and find the importance of 
 group of independent variables to predict the group of dependent variables as well as 
 illustrate the correlation between groups of dependent variables . this study is to realize 
 the effect of sexual functions in stroke patients in computer science point of view . moreover , we applied 10-fold cross - validation for getting better result in multiple linear 
 regressions19 and compared the result 
 of these three methods on our data that we conclude the best result from random forest and 
 boosting algorithm . as a result of questionnaire analysis , duration of illness , age , and education level among 
 8 independent variables strongly affect by other dependent variables which are sexual 
 intercourse and changed muscle , changed sexual function , and changed motor & sensory 
 function . according to analysis the quality of life targeted at stroke patients who have less than 
 1  year duration of illness , the quantitative and qualitative measures of most patients 
 related to sexual life were decreased12 . patients who have more than 1  year duration of illness had the same result14 . this is due to the fact that most stroke 
 patients did not enjoy traveling and an engaging in outdoor activities so that the quality 
 of life was reduced12 . the sexual 
 function of most stroke patients in this study was also reduced because patients and their 
 spouses focused on rehabilitation for the first year after an illness occurred , and there 
 was absence of sex education after one year21 . forsbergwrleby et al.12 pointed out the necessity of sex education for stroke patients and 
 their spouses in terms of the quality of life . appropriate 
 sexual life and sex education according to the duration of illness are also considered 
 important factors to improve the quality of life , and it needs to examine a detailed sexual 
 life and an education based on the seriousness of a stroke in the future . approximately 60% of the stroke patients between 60s and 70s showed reduction of the sexual 
 function with the erectile dysfunction , and it reported the high possibility of the erectile 
 dysfunction as getting old21 . in this 
 study , the sexual activity of the patients between 40s and 50s was reduced after a stroke 
 occurred compared to patients between 60s and 70s . since this referred to the physiological 
 age - related characteristic and they had active sexual life compared to other age groups , 
 variables related to a sexual function were proportionally lower than they were before 
 illness occurred . an education level is categorized according to graduation : before graduating 
 elementary school , graduated from middle school , graduated from high school , and after 
 graduating university . as an education level goes up , it shows that patients who graduated 
 university tend to often have a conversation about the sexual topic , and this group also 
 showed the high statistical result regarding the necessity of a sexual study , sexual 
 intercourse status , and the number of sexual intercourse . this was due to the possibility 
 that they might have more sexual education opportunities so that they could have more 
 chances of sexual intercourse14 , 20 . patients between 60s and 70s did not respond to some 
 questionnaire items due to passive attitude and repulsion . this limitation caused the low 
 response rate so that we had a difficulty to generalize the research result . yet , we found 
 out that sexual education for disabled koreans needed to be developed urgently and hopefully 
 this study would be a good guideline for developing such sexual program . in conclusion , this study found out that duration of illness , age , and education level were 
 important factors that affected patients sexual life and function . it is required to make 
 more specific descriptions of the questionnaire items and needs to complement a 
 questionnaire for the future work .