python matplotlib - 使用meshgrid爲用戶定義的函數進行格式化

Question

我有一個名爲funcPower3的函數，其正文如下所示。我想用MatplotLib中的三維繪圖函數繪製該函數。我看到一個關於meshgrid的scipy文檔的例子。然而，在這個例子中，功能不定義的功能，但一個簡單的數學運算：

fig = plt.figure() 
ax = fig.gca(projection='3d') 
X = np.arange(-5, 5, 0.25) 
Y = np.arange(-5, 5, 0.25) 
X, Y = np.meshgrid(X, Y) 
R = np.sqrt(X**2 + Y**2) 
Z = np.sin(R) 
surf = ax.plot_surface(X, Y, Z, rstride=1, cstride=1, cmap=cm.jet, 
    linewidth=0, antialiased=False) 

我的靈感在此示例中，但我自己的函數簽名不出來meshgrid的數據兼容。我有這樣的錯誤：

ValueError: zero-size array to minimum.reduce without identity 

我的函數的代碼是在這裏：

def funcPower3(PARAM): 
    inputX1 = open("power3X.txt","r") 
    inputY = open("power3Y.txt","r") 
    X1=[] 
    Y=[] 
    for line in inputX1: 
     X1.append(float(line)) 
    for line in inputY: 
     Y.append(float(line)) 
    resTmp_ = 0 
    res = 0 
    for i in range(len(X1)): 
     resTmp_ = Y[i] - (PARAM[0]*(X1[i])**float(PARAM[1])) 
     res += resTmp_**2 
    return res 

和代碼來繪製3D這個功能是在這裏：

XMIN = 0 YMIN = 0 XMAX = 10 ymax = 1

fig = plt.figure('Power 3') 
ax = fig.gca(projection='3d') 
Z = [] 
Xpl = numpy.arange(xmin, xmax, 0.1).tolist() 
Ypl = numpy.arange(ymin, ymax, 0.01).tolist() 
Xpl, Ypl = numpy.meshgrid(Xpl, Ypl) 
Z=[] 
for i in range(len(Xpl[0])): 
    for j in range(len(Xpl)): 
     Z.append(funcPower3([Xpl[j][i],Ypl[j][i]])) 
surf=ax.plot_surface(Xpl, Ypl, Z, rstride=8, cstride=8, alpha=0.3,cmap=cm.jet) 
ax.set_xlabel('X Label') 
ax.set_ylabel('Y Label') 
plt.show() 

謝謝並且會提出任何建議; ））

Answer 1

從plot_surfacedocumentation報價：

X, Y, Z : Data values as 2D arrays

但你Z是一維的。您需要重新調整它以匹配X和Y值。這應該工作：

Xpl = numpy.arange(xmin, xmax, 0.1).tolist() 
Ypl = numpy.arange(ymin, ymax, 0.01).tolist() 
Xpl, Ypl = numpy.meshgrid(Xpl, Ypl) 

Z=[] 
for j in range(len(Xpl)): 
    for i in range(len(Xpl[0])): 
     # your loop order was backwards 
     Z.append(funcPower3([Xpl[j][i],Ypl[j][i]])) 

# reshape Z 
Z = numpy.array(Z).reshape(Xpl.shape) 

fig = plt.figure('Power 3') 
ax = fig.gca(projection='3d') 
surf=ax.plot_surface(Xpl, Ypl, Z, rstride=8, cstride=8, alpha=0.3,cmap=cm.jet) 
ax.set_xlabel('X Label') 
ax.set_ylabel('Y Label') 
plt.show() 

但是你的代碼有一些缺陷。首先，看看你的funcPower3函數，你爲每個函數調用反覆讀取兩個文件。這太浪費了。改爲只讀一次這些參數，並將它們作爲參數提供給您的函數。這個功能也可以簡化一點（和嘗試按照PEP8命名慣例）：

def func_power_3(param, x1, y): 
    p1, p2 = param 
    res = sum(y_i - (p1*x1_i)**p2 for x1_i, y_i in zip(x1, y)) 
    return res 

，其餘的將是

with open("power3X.txt","r") as infile: 
    x1 = [float(line) for line in infile] 

with open("power3Y.txt","r") as infile: 
    y = [float(line) for line in infile] 

xpl = numpy.arange(xmin, xmax, 0.1) # no need for .tolist() 
ypl = numpy.arange(ymin, ymax, 0.01) # meshgrid can work with numpy.array's 
xpl, ypl = numpy.meshgrid(xpl, ypl) 

# we can form z with list comprehension 
z = [[func_power_3([p1,p2], x1, y) for p1, p2 in zip(p1row, p2row)] 
            for p1row, p2row in zip(xpl, ypl)] 

fig = plt.figure('Power 3') 
ax = fig.gca(projection='3d') 
surf=ax.plot_surface(xpl, ypl, z, rstride=8, cstride=8, alpha=0.3,cmap=cm.jet) 
ax.set_xlabel('X Label') 
ax.set_ylabel('Y Label') 
plt.show()