def getResponseTimeAvg(checks):
"""Return the average of the response times
Arguments:
- checks: A dictionary (key: check time) of pingdomcheck.PingdomCheck objects
"""
x, y = PingdomCheck.getArrayData(checks)
avg = 0
for resp_time in y:
avg += resp_time
avg /= len(x)
return avg
def computeLinearRegressionModel(checks):
"""Compute a linear regression model for experimental measures.
The model is a function y' = ax + b which best fit the scatter plot of given experimental measures.
Arguments:
- x, y : vectors (lists) of measures
Return: [a, b], the coefficient of the linear regression model
"""
def sum_vector(n, x):
sum = 0
for i in range(n):
sum += x[i]
return sum
def sum_vector_power(n, x, power):
sum = 0
for i in range(n):
sum += pow(x[i], power)
return sum
def sum_xiyi(n, x, y):
sum = 0
for i in range(n):
sum += x[i] * y[i]
return sum
x, y = PingdomCheck.getArrayData(checks)
n = len(x)
if(n != len(y)):
raise Exception('You must have the same count of measures in x and y vectors.')
a = float((n * sum_xiyi(n, x, y) - sum_vector(n, x) * sum_vector(n, y))) / float((n * sum_vector_power(n, x, 2) - pow(sum_vector(n, x), 2)))
b = float((sum_vector(n, y) * sum_vector_power(n, x, 2) - sum_vector(n, x) * sum_xiyi(n, x, y))) / float((n * sum_vector_power(n, x, 2) - pow(sum_vector(n, x), 2)))
return [a, b]
def plot(
checks,
rep_time_avg,
reg_coef,
response_time_low,
response_time_high,
settlement="",
file="out.ps",
terminal="postscript",
):
"""Plot a graph of the check results.
Arguments:
- checks: dictionary of checks results (see pingdom.PingdomCheck class)
- rep_time_avg: The average response time
- reg_coef: The coefficient of the linear regression model
- response_time_low: The lower bound of response time
- response_time_high: The higher bound of response time
- settlement: (optional; default: blank string) The scaling decision to display on the graph
- file: (optional; default: "out.ps") The destination path+filename of the plotted graph
- terminal (optional; default: "postscript") The file type to use
"""
x, y = PingdomCheck.getArrayData(checks)
checks_count = len(x)
reg_values = []
for time in x:
reg_values.append(reg_coef[0] * time + reg_coef[1])
first_time = x[0]
plot_times = [(time - first_time) for time in x]
checks_graph = Gnuplot.Data(plot_times, y, title="Pingdom checks", with_='lines lc rgb "red" lw 2')
average_graph = Gnuplot.Data(
plot_times, [rep_time_avg] * checks_count, title="Avg. response time", with_='lines lc rgb "green" lw 1'
)
resp_time_low_graph = Gnuplot.Data(
plot_times,
[response_time_low] * checks_count,
title="Resp. time low bound",
with_='lines lc rgb "grey" lw 1',
)
resp_time_high_graph = Gnuplot.Data(
plot_times,
[response_time_high] * checks_count,
title="Resp. time high bound",
with_='lines lc rgb "grey" lw 1',
)
lin_reg_graph = Gnuplot.Data(
plot_times, reg_values, title="Resp. time tendency", with_='lines lc rgb "blue" lw 1'
)
g = Gnuplot.Gnuplot()
g.set_string("output", file)
g("set terminal %s" % terminal)
if settlement != "":
g.set(title="Settlement: " + settlement)
g.xlabel("Time (s)")
g.ylabel("Response time (ms)")
g.plot(checks_graph, average_graph, resp_time_low_graph, resp_time_high_graph, lin_reg_graph)
