词频计算部分

原数据从mysql中获取. 我要统计返回行tag属性中包含的tag词频。

sql_tags_all = "select tags from wbdata;"
cursor.execute(sql_tags_all)
sql_tags_all_result = cursor.fetchall()

返回数据的每一个row都是一个微博对应的5个tag，由空格分开.
接下来把查询到的所有行的tag合并

def turn_tags_tostring(sql_result):
    outputstring = ""
    for row in sql_result:
        longlist = row[0].split(" ")
        for i in range(len(longlist)-1):
            outputstring = outputstring + longlist[i+1] +","
    return outputstring

接下来是对输出的这个string进行词频统计.
这里涉及到后面词云的生成，因此输出上有规范.
已知目标输出格式为一个list，包含了所有出现在词云中的词语，每个词语是一个字典，分别为文字部分和大小，样例为：
[{"text":"德国","size":120},{"text":"motion","size":15},{"text":"forces","size":10}]
因此，在统计完词频后，要将频率转化为size.
在这里，词云词语的大小范围定位10到120.
线性转化方法：

def linear_scale(inputmin,inputmax,outputmin,outputmax,item):
    a = float(outputmax-outputmin)/float(inputmax-inputmin)
    b = outputmax - a*inputmax
    output = a*item +b
    return output

接下来就是输入sting和希望取的前多少位词语，（下面的代码块儿都为一个函数）

def wordscounter(text, n):
    wordDict = {}
    wordlist =text.split(",")
    for word in wordlist:
        if word in wordDict:
            wordDict[word] = wordDict[word] + 1
        else:
            wordDict[word] = 1

然后加入了无关词语过滤，手动去掉高频无关词汇：

    removelist = ["秒拍", "视频", "网页", "分享", "全文", "链接", "00", "01","1", "2", "3", "4", "5", "6", "7", "8", "9", "10", "11",
                  "12", "13", "14", "15","16","17","18","19","20", "21", "22", "23", "24", "25", "26", "27", "28","29", "30","31","100", "20",  "40", "50",
                  "60", "70", "80","90"]//这里添加一个list去掉无关但是频率较高的词语
    for word in removelist:
        try:
            del wordDict[word.decode("utf-8")]
            print "delet", word
        except Exception:
            pass

接下来使用counter方法来进行词频统计，并取得前n位最频繁的词语：

    count = Counter(wordDict)
    rank = count.most_common()[:n]

接下来要使用最开始定义的线性变换方法来计算每个单词的大小了，
因为会有出现数据量小的时候，词频最高的第一位由于是关键词把第二位甩得老远，做出来的词云没有层次不好看，所以在这里，我设定词频最高的第一个词大小恒定位120，从第二名开始到第120名再从110到10进行线性变换.

    countmax = rank[1][1]   //取得最大词频
    countmin = rank[-1][1]  //取得最小词频
    diclist = []
    for item in rank:
        rankdic = {}
        rankdic['text'] = item[0]  //设定文字部分
        rankdic['size'] = functions.linear_scale(countmin,countmax,10,110,item[1])
        diclist.append(rankdic) //调用线性变换方法根据词频得到每个单词的大小
    diclist[0]['size'] = 120  // 把首词大小设为120
    print json.dumps(diclist, encoding="UTF-8", ensure_ascii=False)   //打印中文检查结果

词云部分

包含以下script

  <script src="//d3js.org/d3.v3.min.js"></script>
  <script src="//d3js.org/topojson.v1.min.js"></script>
  <script src="./static/lib/js/d3.layout.cloud.js"></script>

d3.layout.cloud.js在文章最后给出

frequency_list就是上面返回的格式为[{"text":"text", "size":120},{"text":"text", "size":100}]的列表.

   //获得数据
   var frequency_list ={{frequency_list}};

   //设定一个线性非连贯比例尺来进行给不同大小的词赋颜色.
   var color = d3.scale.linear()
            .domain([0,1,2,3,4,5,6,10,15,20,100])
            .range(["#ddd", "#ccc", "#bbb", "#aaa", "#999", "#888", "#777", "#666", "#555", "#444", "#333", "#222"]); 
    
    d3.layout.cloud().size([800, 300])
            .words(frequency_list)
            .rotate(0)
            .fontSize(function(d) { return d.size; })
            .on("end", draw)
            .start();

    function draw(words) {
        d3.select("#word_cloud").append("svg")//根据id选择父对象插入svg
                .attr("width", "100%")
                .attr("height", "100%")
                .attr("viewBox","0 0 900 400")
                .attr("style", "border: 1px solid black")
                .attr("preserveAspectRatio","xMaxYMax meet")
                .attr("class", "wordcloud")
                .append("g")
                .attr("transform", "translate(400,200)")
                .selectAll("text")
                .data(words)
                .enter().append("text")
                .style("font-size", function(d) { return d.size + "px"; })
                .style("fill", function(d, i) { return color(i); })
                .attr("transform", function(d) {
                    return "translate(" + [d.x, d.y] + ")rotate(" + d.rotate + ")";
                })
                .text(function(d) { return d.text; });
    }

到此，首图上的词云就应该可以实现啦~
:)

d3.layout.cloud.js

// Word cloud layout by Jason Davies, http://www.jasondavies.com/word-cloud/
// Algorithm due to Jonathan Feinberg, http://static.mrfeinberg.com/bv_ch03.pdf
(function(exports) {
    function cloud() {
        var size = [256, 256],
            text = cloudText,
            font = cloudFont,
            fontSize = cloudFontSize,
            fontStyle = cloudFontNormal,
            fontWeight = cloudFontNormal,
            rotate = cloudRotate,
            padding = cloudPadding,
            spiral = archimedeanSpiral,
            words = [],
            timeInterval = Infinity,
            event = d3.dispatch("word", "end"),
            timer = null,
            cloud = {};

        cloud.start = function() {
            var board = zeroArray((size[0] >> 5) * size[1]),
                bounds = null,
                n = words.length,
                i = -1,
                tags = [],
                data = words.map(function(d, i) {
                    d.text = text.call(this, d, i);
                    d.font = font.call(this, d, i);
                    d.style = fontStyle.call(this, d, i);
                    d.weight = fontWeight.call(this, d, i);
                    d.rotate = rotate.call(this, d, i);
                    d.size = ~~fontSize.call(this, d, i);
                    d.padding = padding.call(this, d, i);
                    return d;
                }).sort(function(a, b) { return b.size - a.size; });

            if (timer) clearInterval(timer);
            timer = setInterval(step, 0);
            step();

            return cloud;

            function step() {
                var start = +new Date,
                    d;
                while (+new Date - start < timeInterval && ++i < n && timer) {
                    d = data[i];
                    d.x = (size[0] * (Math.random() + .5)) >> 1;
                    d.y = (size[1] * (Math.random() + .5)) >> 1;
                    cloudSprite(d, data, i);
                    if (d.hasText && place(board, d, bounds)) {
                        tags.push(d);
                        event.word(d);
                        if (bounds) cloudBounds(bounds, d);
                        else bounds = [{x: d.x + d.x0, y: d.y + d.y0}, {x: d.x + d.x1, y: d.y + d.y1}];
                        // Temporary hack
                        d.x -= size[0] >> 1;
                        d.y -= size[1] >> 1;
                    }
                }
                if (i >= n) {
                    cloud.stop();
                    event.end(tags, bounds);
                }
            }
        }

        cloud.stop = function() {
            if (timer) {
                clearInterval(timer);
                timer = null;
            }
            return cloud;
        };

        cloud.timeInterval = function(x) {
            if (!arguments.length) return timeInterval;
            timeInterval = x == null ? Infinity : x;
            return cloud;
        };

        function place(board, tag, bounds) {
            var perimeter = [{x: 0, y: 0}, {x: size[0], y: size[1]}],
                startX = tag.x,
                startY = tag.y,
                maxDelta = Math.sqrt(size[0] * size[0] + size[1] * size[1]),
                s = spiral(size),
                dt = Math.random() < .5 ? 1 : -1,
                t = -dt,
                dxdy,
                dx,
                dy;

            while (dxdy = s(t += dt)) {
                dx = ~~dxdy[0];
                dy = ~~dxdy[1];

                if (Math.min(dx, dy) > maxDelta) break;

                tag.x = startX + dx;
                tag.y = startY + dy;

                if (tag.x + tag.x0 < 0 || tag.y + tag.y0 < 0 ||
                    tag.x + tag.x1 > size[0] || tag.y + tag.y1 > size[1]) continue;
                // TODO only check for collisions within current bounds.
                if (!bounds || !cloudCollide(tag, board, size[0])) {
                    if (!bounds || collideRects(tag, bounds)) {
                        var sprite = tag.sprite,
                            w = tag.width >> 5,
                            sw = size[0] >> 5,
                            lx = tag.x - (w << 4),
                            sx = lx & 0x7f,
                            msx = 32 - sx,
                            h = tag.y1 - tag.y0,
                            x = (tag.y + tag.y0) * sw + (lx >> 5),
                            last;
                        for (var j = 0; j < h; j++) {
                            last = 0;
                            for (var i = 0; i <= w; i++) {
                                board[x + i] |= (last << msx) | (i < w ? (last = sprite[j * w + i]) >>> sx : 0);
                            }
                            x += sw;
                        }
                        delete tag.sprite;
                        return true;
                    }
                }
            }
            return false;
        }

        cloud.words = function(x) {
            if (!arguments.length) return words;
            words = x;
            return cloud;
        };

        cloud.size = function(x) {
            if (!arguments.length) return size;
            size = [+x[0], +x[1]];
            return cloud;
        };

        cloud.font = function(x) {
            if (!arguments.length) return font;
            font = d3.functor(x);
            return cloud;
        };

        cloud.fontStyle = function(x) {
            if (!arguments.length) return fontStyle;
            fontStyle = d3.functor(x);
            return cloud;
        };

        cloud.fontWeight = function(x) {
            if (!arguments.length) return fontWeight;
            fontWeight = d3.functor(x);
            return cloud;
        };

        cloud.rotate = function(x) {
            if (!arguments.length) return rotate;
            rotate = d3.functor(x);
            return cloud;
        };

        cloud.text = function(x) {
            if (!arguments.length) return text;
            text = d3.functor(x);
            return cloud;
        };

        cloud.spiral = function(x) {
            if (!arguments.length) return spiral;
            spiral = spirals[x + ""] || x;
            return cloud;
        };

        cloud.fontSize = function(x) {
            if (!arguments.length) return fontSize;
            fontSize = d3.functor(x);
            return cloud;
        };

        cloud.padding = function(x) {
            if (!arguments.length) return padding;
            padding = d3.functor(x);
            return cloud;
        };

        return d3.rebind(cloud, event, "on");
    }

    function cloudText(d) {
        return d.text;
    }

    function cloudFont() {
        return "serif";
    }

    function cloudFontNormal() {
        return "normal";
    }

    function cloudFontSize(d) {
        return Math.sqrt(d.value);
    }

    function cloudRotate() {
        return (~~(Math.random() * 6) - 3) * 30;
    }

    function cloudPadding() {
        return 1;
    }

    // Fetches a monochrome sprite bitmap for the specified text.
    // Load in batches for speed.
    function cloudSprite(d, data, di) {
        if (d.sprite) return;
        c.clearRect(0, 0, (cw << 5) / ratio, ch / ratio);
        var x = 0,
            y = 0,
            maxh = 0,
            n = data.length;
        --di;
        while (++di < n) {
            d = data[di];
            c.save();
            c.font = d.style + " " + d.weight + " " + ~~((d.size + 1) / ratio) + "px " + d.font;
            var w = c.measureText(d.text + "m").width * ratio,
                h = d.size << 1;
            if (d.rotate) {
                var sr = Math.sin(d.rotate * cloudRadians),
                    cr = Math.cos(d.rotate * cloudRadians),
                    wcr = w * cr,
                    wsr = w * sr,
                    hcr = h * cr,
                    hsr = h * sr;
                w = (Math.max(Math.abs(wcr + hsr), Math.abs(wcr - hsr)) + 0x1f) >> 5 << 5;
                h = ~~Math.max(Math.abs(wsr + hcr), Math.abs(wsr - hcr));
            } else {
                w = (w + 0x1f) >> 5 << 5;
            }
            if (h > maxh) maxh = h;
            if (x + w >= (cw << 5)) {
                x = 0;
                y += maxh;
                maxh = 0;
            }
            if (y + h >= ch) break;
            c.translate((x + (w >> 1)) / ratio, (y + (h >> 1)) / ratio);
            if (d.rotate) c.rotate(d.rotate * cloudRadians);
            c.fillText(d.text, 0, 0);
            if (d.padding) c.lineWidth = 2 * d.padding, c.strokeText(d.text, 0, 0);
            c.restore();
            d.width = w;
            d.height = h;
            d.xoff = x;
            d.yoff = y;
            d.x1 = w >> 1;
            d.y1 = h >> 1;
            d.x0 = -d.x1;
            d.y0 = -d.y1;
            d.hasText = true;
            x += w;
        }
        var pixels = c.getImageData(0, 0, (cw << 5) / ratio, ch / ratio).data,
            sprite = [];
        while (--di >= 0) {
            d = data[di];
            if (!d.hasText) continue;
            var w = d.width,
                w32 = w >> 5,
                h = d.y1 - d.y0;
            // Zero the buffer
            for (var i = 0; i < h * w32; i++) sprite[i] = 0;
            x = d.xoff;
            if (x == null) return;
            y = d.yoff;
            var seen = 0,
                seenRow = -1;
            for (var j = 0; j < h; j++) {
                for (var i = 0; i < w; i++) {
                    var k = w32 * j + (i >> 5),
                        m = pixels[((y + j) * (cw << 5) + (x + i)) << 2] ? 1 << (31 - (i % 32)) : 0;
                    sprite[k] |= m;
                    seen |= m;
                }
                if (seen) seenRow = j;
                else {
                    d.y0++;
                    h--;
                    j--;
                    y++;
                }
            }
            d.y1 = d.y0 + seenRow;
            d.sprite = sprite.slice(0, (d.y1 - d.y0) * w32);
        }
    }

    // Use mask-based collision detection.
    function cloudCollide(tag, board, sw) {
        sw >>= 5;
        var sprite = tag.sprite,
            w = tag.width >> 5,
            lx = tag.x - (w << 4),
            sx = lx & 0x7f,
            msx = 32 - sx,
            h = tag.y1 - tag.y0,
            x = (tag.y + tag.y0) * sw + (lx >> 5),
            last;
        for (var j = 0; j < h; j++) {
            last = 0;
            for (var i = 0; i <= w; i++) {
                if (((last << msx) | (i < w ? (last = sprite[j * w + i]) >>> sx : 0))
                    & board[x + i]) return true;
            }
            x += sw;
        }
        return false;
    }

    function cloudBounds(bounds, d) {
        var b0 = bounds[0],
            b1 = bounds[1];
        if (d.x + d.x0 < b0.x) b0.x = d.x + d.x0;
        if (d.y + d.y0 < b0.y) b0.y = d.y + d.y0;
        if (d.x + d.x1 > b1.x) b1.x = d.x + d.x1;
        if (d.y + d.y1 > b1.y) b1.y = d.y + d.y1;
    }

    function collideRects(a, b) {
        return a.x + a.x1 > b[0].x && a.x + a.x0 < b[1].x && a.y + a.y1 > b[0].y && a.y + a.y0 < b[1].y;
    }

    function archimedeanSpiral(size) {
        var e = size[0] / size[1];
        return function(t) {
            return [e * (t *= .1) * Math.cos(t), t * Math.sin(t)];
        };
    }

    function rectangularSpiral(size) {
        var dy = 4,
            dx = dy * size[0] / size[1],
            x = 0,
            y = 0;
        return function(t) {
            var sign = t < 0 ? -1 : 1;
            // See triangular numbers: T_n = n * (n + 1) / 2.
            switch ((Math.sqrt(1 + 4 * sign * t) - sign) & 3) {
                case 0:  x += dx; break;
                case 1:  y += dy; break;
                case 2:  x -= dx; break;
                default: y -= dy; break;
            }
            return [x, y];
        };
    }

    // TODO reuse arrays?
    function zeroArray(n) {
        var a = [],
            i = -1;
        while (++i < n) a[i] = 0;
        return a;
    }

    var cloudRadians = Math.PI / 180,
        cw = 1 << 11 >> 5,
        ch = 1 << 11,
        canvas,
        ratio = 1;

    if (typeof document !== "undefined") {
        canvas = document.createElement("canvas");
        canvas.width = 1;
        canvas.height = 1;
        ratio = Math.sqrt(canvas.getContext("2d").getImageData(0, 0, 1, 1).data.length >> 2);
        canvas.width = (cw << 5) / ratio;
        canvas.height = ch / ratio;
    } else {
        // node-canvas support
        var Canvas = require("canvas");
        canvas = new Canvas(cw << 5, ch);
    }

    var c = canvas.getContext("2d"),
        spirals = {
            archimedean: archimedeanSpiral,
            rectangular: rectangularSpiral
        };
    c.fillStyle = c.strokeStyle = "red";
    c.textAlign = "center";

    exports.cloud = cloud;
})(typeof exports === "undefined" ? d3.layout || (d3.layout = {}) : exports);