SAS统计一篇文章中各字母的出现频率

data;
    TEXT="It is Teacher's Day today. On this special occasion I would like to extend my heartfelt congratulations to all teachers, Happy Teacher's Day! Of all teachers who have taught me since my early childhood, the most unforgettable one is my first English teacher in college, Ms. Zhang. It is she who has aroused my keen interest in the learning of English and helped me realize the importance of self-reliance. Born into a poor farmer's family in a mountainous area and educated in relatively primitive surroundings, I found myself lagging far behind in the first class in college, which happened to be Ms. Zhang's English class. I was really discouraged and frustrated, so I decided to drop out. Ms. Zhang was so keenly insightful that she had noticed my embarrassment in class. After class, she called me into the Teacher's Room and discussed the situation with me, earnestly and kindly, citing the example of Robinson Crusoe to motivate me to go ahead in spite of all kinds of difficulties. Be a man and rely on yourself, she nudged me. The next time we met, she brought me a simplified version of Robinson Crusoe and recommended that I finish reading it in a week and write a book report. Under her consistent and patient guidance, not only has my English been greatly improved, but my confidence and courage enhanced considerably. Rely on yourself and be a man, Ms. Zhang's inspiring words have been echoing in my mind. I will work harder and try my utmost to lay a solid foundation for my future career. Only by so doing can I repay Ms. Zhang's kindness and live up to her expectations of me, that is, to become a useful person and contribute to society.";
    i=1;
    do until(scan(TEXT, i)='');
        WORD=scan(TEXT, i);
        output;
        i+1;
    end;
run;

proc freq;
    tables WORD / noprint out=counts;
run;

data demo;
    TEXT="It is Teacher's Day today. On this special occasion I would like to extend my heartfelt congratulations to all teachers, Happy Teacher's Day! Of all teachers who have taught me since my early childhood, the most unforgettable one is my first English teacher in college, Ms. Zhang. It is she who has aroused my keen interest in the learning of English and helped me realize the importance of self-reliance. Born into a poor farmer's family in a mountainous area and educated in relatively primitive surroundings, I found myself lagging far behind in the first class in college, which happened to be Ms. Zhang's English class. I was really discouraged and frustrated, so I decided to drop out. Ms. Zhang was so keenly insightful that she had noticed my embarrassment in class. After class, she called me into the Teacher's Room and discussed the situation with me, earnestly and kindly, citing the example of Robinson Crusoe to motivate me to go ahead in spite of all kinds of difficulties. Be a man and rely on yourself, she nudged me. The next time we met, she brought me a simplified version of Robinson Crusoe and recommended that I finish reading it in a week and write a book report. Under her consistent and patient guidance, not only has my English been greatly improved, but my confidence and courage enhanced considerably. Rely on yourself and be a man, Ms. Zhang's inspiring words have been echoing in my mind. I will work harder and try my utmost to lay a solid foundation for my future career. Only by so doing can I repay Ms. Zhang's kindness and live up to her expectations of me, that is, to become a useful person and contribute to society.";
    TEXT_TEMP=TEXT;
    if _N_=1 then do;
        RE1=prxparse('s/(\b.+?\b)(\s.*?)(\b\1+\b)/\2\3/i');
        RE2=prxparse('/(\b.+?\b)(\s.*?)(\b\1+\b)/i');
    end;
    /*Remove repeated values*/
    do i=1 to 1000;
        TEXT=prxchange(RE1, -1, cats(TEXT));
        if not prxmatch(RE2, cats(TEXT)) then leave;
    end;
    do i=1 to countw(TEXT);
        WORD=scan(TEXT, i);
        COUNT=0;
        RE=prxparse('/\b'||cats(WORD)||'\b/i');
        START=1;
        STOP=length(TEXT_TEMP);
        call prxnext(RE, START, STOP, TEXT_TEMP, POSITION, LENGTH);
        do while(POSITION>0);
            COUNT+1;
            call prxnext(RE, START, STOP, TEXT_TEMP, POSITION, LENGTH);
        end;
        FREQ=COUNT/countw(TEXT_TEMP)*100;
        keep WORD COUNT FREQ;
        output;
    end;
run;

data demo;
    TEXT="It is Teacher's Day today. On this special occasion I would like to extend my heartfelt congratulations to all teachers, Happy Teacher's Day! Of all teachers who have taught me since my early childhood, the most unforgettable one is my first English teacher in college, Ms. Zhang. It is she who has aroused my keen interest in the learning of English and helped me realize the importance of self-reliance. Born into a poor farmer's family in a mountainous area and educated in relatively primitive surroundings, I found myself lagging far behind in the first class in college, which happened to be Ms. Zhang's English class. I was really discouraged and frustrated, so I decided to drop out. Ms. Zhang was so keenly insightful that she had noticed my embarrassment in class. After class, she called me into the Teacher's Room and discussed the situation with me, earnestly and kindly, citing the example of Robinson Crusoe to motivate me to go ahead in spite of all kinds of difficulties. Be a man and rely on yourself, she nudged me. The next time we met, she brought me a simplified version of Robinson Crusoe and recommended that I finish reading it in a week and write a book report. Under her consistent and patient guidance, not only has my English been greatly improved, but my confidence and courage enhanced considerably. Rely on yourself and be a man, Ms. Zhang's inspiring words have been echoing in my mind. I will work harder and try my utmost to lay a solid foundation for my future career. Only by so doing can I repay Ms. Zhang's kindness and live up to her expectations of me, that is, to become a useful person and contribute to society.";
    do i=1 to 26;
        CHAR=byte(i+64);
        COUNT=0;
        RE=prxparse('/'||CHAR||'/i');
        START=1;
        STOP=length(TEXT);
        call prxnext(RE, START, STOP, TEXT, POSITION, LENGTH);
        do while(POSITION>0);
            COUNT+1;
            call prxnext(RE, START, STOP, TEXT, POSITION, LENGTH);
        end;
        if COUNT>0 then do;
            FREQ=COUNT/length(compress(prxchange('s/\W//', -1, TEXT)))*100;
            output;
        end;
    end;
    keep CHAR COUNT FREQ;
run;

data demo;
    TEXT="It is Teacher's Day today. On this special occasion I would like to extend my heartfelt congratulations to all teachers, Happy Teacher's Day! Of all teachers who have taught me since my early childhood, the most unforgettable one is my first English teacher in college, Ms. Zhang. It is she who has aroused my keen interest in the learning of English and helped me realize the importance of self-reliance. Born into a poor farmer's family in a mountainous area and educated in relatively primitive surroundings, I found myself lagging far behind in the first class in college, which happened to be Ms. Zhang's English class. I was really discouraged and frustrated, so I decided to drop out. Ms. Zhang was so keenly insightful that she had noticed my embarrassment in class. After class, she called me into the Teacher's Room and discussed the situation with me, earnestly and kindly, citing the example of Robinson Crusoe to motivate me to go ahead in spite of all kinds of difficulties. Be a man and rely on yourself, she nudged me. The next time we met, she brought me a simplified version of Robinson Crusoe and recommended that I finish reading it in a week and write a book report. Under her consistent and patient guidance, not only has my English been greatly improved, but my confidence and courage enhanced considerably. Rely on yourself and be a man, Ms. Zhang's inspiring words have been echoing in my mind. I will work harder and try my utmost to lay a solid foundation for my future career. Only by so doing can I repay Ms. Zhang's kindness and live up to her expectations of me, that is, to become a useful person and contribute to society.";
    do i=1 to 26;
        CHAR=byte(i+64);
        COUNT=countc(TEXT, CHAR, 'i');
        if COUNT>0 then do;
            FREQ=COUNT/length(compress(prxchange('s/\W//', -1, TEXT)))*100;
            output;
        end;
    end;
    keep CHAR COUNT FREQ;
run;