python 共分散

Question

平均，分散，共分散を求めたいのですが，

xs = []
ys = []
files = glob.glob("./tras/*")
for i, f in enumerate(files):
    img = cv2.imread(f)
    gray = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY)
    ret, binary = cv2.threshold(gray, 0, 255, cv2.THRESH_BINARY_INV + cv2.THRESH_OTSU)
    kernel = cv2.getStructuringElement(cv2.MORPH_ELLIPSE, (5, 5))
    binary = cv2.dilate(binary, kernel)
    contours, hierarchy = cv2.findContours(binary, cv2.RETR_EXTERNAL, cv2.CHAIN_APPROX_SIMPLE)
    target_contour = max(contours, key=lambda x: cv2.contourArea(x))
    area = cv2.contourArea(target_contour)
    retval = cv2.arcLength(target_contour, True)
    ratio=area/retval
    xs.append(ratio)

    hsv = cv2.cvtColor(img, cv2.COLOR_BGR2HSV)
    h, s, v = cv2.split(hsv)
    v=v[10 < v ]
    value = v [ v < 225].mean()
    ys.append(value)



xt = []
yt = []

files = glob.glob("./sisaku-pu/*")
for i, f in enumerate(files):
    img = cv2.imread(f)
    save_path = './pura/_%d.jpg' % i
    cv2.imwrite(save_path, img)
    gray = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY)
    ret, binary = cv2.threshold(gray, 0, 255, cv2.THRESH_BINARY_INV + cv2.THRESH_OTSU)
    kernel = cv2.getStructuringElement(cv2.MORPH_ELLIPSE, (5, 5))
    binary = cv2.dilate(binary, kernel)
    contours, hierarchy = cv2.findContours(binary, cv2.RETR_EXTERNAL, cv2.CHAIN_APPROX_SIMPLE)
    target_contour = max(contours, key=lambda x: cv2.contourArea(x))
    area = cv2.contourArea(target_contour)
    retval = cv2.arcLength(target_contour, True)
    ratio=area/retval
    xt.append(ratio)


    hsv = cv2.cvtColor(img, cv2.COLOR_BGR2HSV)
    h, s, v = cv2.split(hsv)
    v=v[10 < v ]
    value = v [ v < 225].mean()
    yt.append(value)

xst =xt+xs
yst =yt+ys


s = sum(xt)
N = len(xt)
mxt = s / N
print('平均: {0:.4f}'.format(mxt))

s = sum(yt)
N = len(yt)
myt = s / N
print('平均: {0:.4f}'.format(myt))

s = sum(xs)
N = len(xs)
mxs= s / N
print('平均: {0:.4f}'.format(mxs))

s = sum(ys)
N = len(ys)
mys = s / N
print('平均: {0:.4f}'.format(mys))


mxst = mean(xst)
variancexst =np.var(xst, ddof=1)
print('平均: {0:.4f}'.format(mxst))
print('分散: {0:.4f}'.format(variancexst))

myst = mean(yst)
varianceyst =np.var(yst, ddof=1)
print('平均: {0:.4f}'.format(myst))
print('分散: {0:.4f}'.format(varianceyst))
コード

xs,ys,xt,yt,xst,ystの平均値，xst,ystの分散までは求められたのですが，
xst,ystの共分散が求められません。

どなたかよろしくお願いします。

Answer 1

np.cov(xst, yst, ddof=1)[0, 1]ということでしょうか。

numpy.cov — NumPy v1.17 Manual