Pythonで画像を持つモデル(ここでは2Dガウスですが、それは別のものかもしれません)に合わせたいと思います。Pythonのモデルに2Dモデルをフィットする
使用しようとしていますscipy.optimize.curve_fit
私はいくつか質問があります。下記参照。
は、いくつかの機能で始まるのをしてみましょう:
import numpy as np
from scipy.optimize import curve_fit
from scipy.signal import argrelmax
import matplotlib.pyplot as plt
from matplotlib import cm
from matplotlib.patches import Circle
from tifffile import TiffFile
# 2D Gaussian model
def func(xy, x0, y0, sigma, H):
x, y = xy
A = 1/(2 * sigma**2)
I = H * np.exp(-A * ((x - x0)**2 + (y - y0)**2))
return I
# Generate 2D gaussian
def generate(x0, y0, sigma, H):
x = np.arange(0, max(x0, y0) * 2 + sigma, 1)
y = np.arange(0, max(x0, y0) * 2 + sigma, 1)
xx, yy = np.meshgrid(x, y)
I = func((xx, yy), x0=x0, y0=y0, sigma=sigma, H=H)
return xx, yy, I
def fit(image, with_bounds):
# Prepare fitting
x = np.arange(0, image.shape[1], 1)
y = np.arange(0, image.shape[0], 1)
xx, yy = np.meshgrid(x, y)
# Guess intial parameters
x0 = int(image.shape[0]) # Middle of the image
y0 = int(image.shape[1]) # Middle of the image
sigma = max(*image.shape) * 0.1 # 10% of the image
H = np.max(image) # Maximum value of the image
initial_guess = [x0, y0, sigma, H]
# Constraints of the parameters
if with_bounds:
lower = [0, 0, 0, 0]
upper = [image.shape[0], image.shape[1], max(*image.shape), image.max() * 2]
bounds = [lower, upper]
else:
bounds = [-np.inf, np.inf]
pred_params, uncert_cov = curve_fit(func, (xx.ravel(), yy.ravel()), image.ravel(),
p0=initial_guess, bounds=bounds)
# Get residual
predictions = func((xx, yy), *pred_params)
rms = np.sqrt(np.mean((image.ravel() - predictions.ravel())**2))
print("True params : ", true_parameters)
print("Predicted params : ", pred_params)
print("Residual : ", rms)
return pred_params
def plot(image, params):
fig, ax = plt.subplots()
ax.imshow(image, cmap=plt.cm.BrBG, interpolation='nearest', origin='lower')
ax.scatter(params[0], params[1], s=100, c="red", marker="x")
circle = Circle((params[0], params[1]), params[2], facecolor='none',
edgecolor="red", linewidth=1, alpha=0.8)
ax.add_patch(circle)
# Simulate and fit model
true_parameters = [50, 60, 10, 500]
xx, yy, image = generate(*true_parameters)
# The fit performs well without bounds
params = fit(image, with_bounds=False)
plot(image, params)
出力:今
True params : [50, 60, 10, 500]
Predicted params : [ 50. 60. 10. 500.]
Residual : 0.0
我々は境界(または制約)と同じフィット感をすれば。
# The fit is really bad with bounds
params = fit(image, with_bounds=True)
plot(image, params)
出力:私は境界を追加するときにフィットがうまく行っていないのはなぜ
True params : [50, 60, 10, 500]
Predicted params : [ 130. 130. 0.72018729 1.44948159]
Residual : 68.1713019773
?
私は理解できません。実際のデータに適用した場合、このフィット感が強くないのはなぜですか?下記参照。
# Load some real data
image = TiffFile("../data/spot.tif").asarray()
plt.imshow(image, aspect='equal', origin='lower', interpolation="none", cmap=plt.cm.BrBG)
plt.colorbar()
# Fit is not possible without bounds
params = fit(image, with_bounds=False)
plot(image, params)
出力:
---------------------------------------------------------------------------
RuntimeError Traceback (most recent call last)
<ipython-input-14-3187b53d622d> in <module>()
1 # Fit is not possible without bounds
----> 2 params = fit(image, with_bounds=False)
3 plot(image, params)
<ipython-input-11-f14c9dec72f2> in fit(image, with_bounds)
54
55 pred_params, uncert_cov = curve_fit(func, (xx.ravel(), yy.ravel()), image.ravel(),
---> 56 p0=initial_guess, bounds=bounds)
57
58 # Get residual
/home/hadim/local/conda/envs/ws/lib/python3.5/site-packages/scipy/optimize/minpack.py in curve_fit(f, xdata, ydata, p0, sigma, absolute_sigma, check_finite, bounds, method, **kwargs)
653 cost = np.sum(infodict['fvec'] ** 2)
654 if ier not in [1, 2, 3, 4]:
--> 655 raise RuntimeError("Optimal parameters not found: " + errmsg)
656 else:
657 res = least_squares(func, p0, args=args, bounds=bounds, method=method,
RuntimeError: Optimal parameters not found: Number of calls to function has reached maxfev = 1000.
そして
# Fit works but is not accurate at all with bounds
params = fit(image, with_bounds=True)
plot(image, params)
出力:
True params : [50, 60, 10, 500]
Predicted params : [ 19.31770886 10.52153346 37. 1296.22524248]
Residual : 83.1944464761
偽のデータに 'image + = np.random.normal(loc = 0、scale = 1e-2、size = image.shape)'というノイズを追加することで、実際のデータケースを再現することもできます。 – HadiM