#Рисование графика.
        plot = Gnuplot(persist = True)
        plot('set contour base')
        plot('set view 0,0')
        plot('set cntrparam levels auto')
        plot('set xrange [' + str(xMin[0]) + ':' + str(xMax[0]) + ']')
        plot('set yrange [' + str(xMin[1]) + ':' + str(xMax[1]) + ']')
        plot('set surface')
        x1s = []
        x2s = []
        fs = []
        for item in history:
            x1s.append(item['x'][0])
            x2s.append(item['x'][1])
            fs.append(item['f'])
        data = Data(x1s, x2s, fs, with_ = 'linespoints 3 3')
        del x1s
        del x2s
        del fs
        plot.splot(str(self.functionLineEdit.text()).replace('x1', 'x').replace('x2', 'y'), data)