Numpy.ndarray-hstack function-Python

# |E|^2 Plot
import csv
newarray=np.zeros((114,1))
for ind,wvln in enumerate(plotWavelengths):
 xData = x_pos
 # get index
 nind  = np.where(lambdas==wvln)[0]
 yData = abs(E[:,nind])**2
 label = '%s nm' % wvln
 eplt.plot(xData,yData,label=label)
 newarray=np.hstack((newarray,yData))
np.savetxt("E squre.csv", newarray, delimiter=",")