/// default constructor
public SignalToNoiseEstimatorMedian() {
setName("SignalToNoiseEstimatorMedian");
defaults_.setValue(
"MaxIntensity",
-1.,
"maximal intensity considered for histogram construction. By default, it will be calculated automatically (see AutoMode)."
+ " Only provide this parameter if you know what you are doing (and change 'AutoMode' to '-1')!"
+ " All intensities EQUAL/ABOVE 'MaxIntensity' will be added to the LAST histogram bin."
+ " If you choose 'MaxIntensity' too small, the noise estimate might be too small as well. "
+ " If chosen too big, the bins become quite large (which you could counter by increasing 'BinCount', which increases runtime)."
+ " In general, the Median-S/N estimator is more robust to a manual MaxIntensity than the MeanIterative-S/N.");
defaults_.setValue(
"AutoMaxStdevFactor",
3.0,
"parameter for 'MaxIntensity' estimation (if 'AutoMode' == 0): mean + 'AutoMaxStdevFactor' * stdev");
defaults_.setValue(
"AutoMaxPercentile",
95,
"parameter for 'MaxIntensity' estimation (if 'AutoMode' == 1): AutoMaxPercentile th percentile");
defaults_.setValue(
"AutoMode",
0,
"method to use to determine maximal intensity: -1 --> use 'MaxIntensity'; 0 --> 'AutoMaxStdevFactor' method (default); 1 --> 'AutoMaxPercentile' method");
defaults_.setValue("WinLen", 200.0, "window length in Thomson");
defaults_.setValue("BinCount", 30, "number of bins used for histogram");
defaults_.setValue(
"MinRequiredElements",
10,
"minimum number of elements required in a window (otherwise it is considered sparse)");
defaults_.setValue(
"NoiseForEmptyWindow", Math.pow(10.0, 20), "noise value used for sparse windows");
defaultsToParam_();
}
/// calculate StN values for all datapoints given, by using a sliding window approach
/// @param scan_first_ first element in the scan
/// @param scan_last_ last element in the scan (disregarded)
protected void computeSTN_(Peak[] data_, int scan_first_, int scan_last_) throws Exception {
// reset counter for sparse windows
double sparse_window_percent = 0;
// reset counter for histogram overflow
double histogram_oob_percent = 0;
// reset the results
stn_estimates_.clear();
// maximal range of histogram needs to be calculated first
if (auto_mode_ == AUTOMAXBYSTDEV) {
// use MEAN+auto_max_intensity_*STDEV as threshold
GaussianEstimate gauss_global = estimate_(data_, scan_first_, scan_last_);
max_intensity_ =
gauss_global.mean + Math.sqrt(gauss_global.variance) * auto_max_stdev_factor_;
} else if (auto_mode_ == AUTOMAXBYPERCENT) {
// get value at "auto_max_percentile_"th percentile
// we use a histogram approach here as well.
if ((auto_max_percentile_ < 0) || (auto_max_percentile_ > 100)) {
String s = "" + auto_max_percentile_;
throw new Exception(
"AutoMode is on AUTOMAXBYPERCENT! AutoMaxPercentile is not in [0,100]. Use setAutoMaxPercentile(<value>) to change it!");
}
int[] histogram_auto = new int[100];
Arrays.fill(histogram_auto, 0);
// find maximum of current scan
int size = 0;
double maxInt = 0;
int run = scan_first_;
while (run != scan_last_) {
maxInt = Math.max(maxInt, data_[run].getIntensity());
++size;
++run;
}
double bin_size = maxInt / 100;
// fill histogram
run = scan_first_;
while (run != scan_last_) {
++histogram_auto[(int) ((data_[run].getIntensity() - 1) / bin_size)];
++run;
}
// add up element counts in histogram until ?th percentile is reached
int elements_below_percentile = (int) (auto_max_percentile_ * size / 100);
int elements_seen = 0;
int i = -1;
run = scan_first_;
while (run != scan_last_ && elements_seen < elements_below_percentile) {
++i;
elements_seen += histogram_auto[i];
++run;
}
max_intensity_ = (((double) i) + 0.5) * bin_size;
} else { // if (auto_mode_ == MANUAL)
if (max_intensity_ <= 0) {
String s = "" + max_intensity_;
throw new Exception(
"AutoMode is on MANUAL! MaxIntensity is <=0. Needs to be positive! Use setMaxIntensity(<value>) or enable AutoMode!");
}
}
if (max_intensity_ <= 0) {
System.err.println(
"TODO SignalToNoiseEstimatorMedian: the max_intensity_ value should be positive! "
+ max_intensity_);
return;
}
int window_pos_center = scan_first_;
int window_pos_borderleft = scan_first_;
int window_pos_borderright = scan_first_;
double window_half_size = win_len_ / 2;
double bin_size = max_intensity_ / bin_count_;
int bin_count_minus_1 = bin_count_ - 1;
int[] histogram = new int[bin_count_];
Arrays.fill(histogram, 0);
double[] bin_value = new double[bin_count_];
Arrays.fill(bin_value, 0.);
// calculate average intensity that is represented by a bin
for (int bin = 0; bin < bin_count_; bin++) {
histogram[bin] = 0;
bin_value[bin] = (bin + 0.5) * bin_size;
}
// bin in which a datapoint would fall
int to_bin = 0;
// index of bin where the median is located
int median_bin = 0;
// additive number of elements from left to x in histogram
int element_inc_count = 0;
// tracks elements in current window, which may vary because of uneven spaced data
int elements_in_window = 0;
// number of windows
int window_count = 0;
// number of elements where we find the median
int element_in_window_half = 0;
double noise; // noise value of a datapoint
// determine how many elements we need to estimate (for progress estimation)
int windows_overall = 0;
int run = scan_first_;
while (run != scan_last_) {
++windows_overall;
++run;
}
// MAIN LOOP
while (window_pos_center != scan_last_) {
// erase all elements from histogram that will leave the window on the LEFT side
while (data_[window_pos_borderleft].getMZ()
< data_[window_pos_center].getMZ() - window_half_size) {
to_bin =
Math.min(
(int) ((data_[window_pos_borderleft].getIntensity()) / bin_size),
bin_count_minus_1);
--histogram[to_bin];
--elements_in_window;
++window_pos_borderleft;
}
// add all elements to histogram that will enter the window on the RIGHT side
while ((window_pos_borderright != scan_last_)
&& (data_[window_pos_borderright].getMZ()
<= data_[window_pos_center].getMZ() + window_half_size)) {
to_bin =
Math.min(
(int) ((data_[window_pos_borderright].getIntensity()) / bin_size),
bin_count_minus_1);
++histogram[to_bin];
++elements_in_window;
++window_pos_borderright;
}
if (elements_in_window < min_required_elements_) {
noise = noise_for_empty_window_;
++sparse_window_percent;
} else {
// find bin i where ceil[elements_in_window/2] <= sum_c(0..i){ histogram[c] }
median_bin = -1;
element_inc_count = 0;
element_in_window_half = (elements_in_window + 1) / 2;
while (median_bin < bin_count_minus_1 && element_inc_count < element_in_window_half) {
++median_bin;
element_inc_count += histogram[median_bin];
}
// increase the error count
if (median_bin == bin_count_minus_1) ++histogram_oob_percent;
// just avoid division by 0
noise = Math.max(1.0, bin_value[median_bin]);
}
// store result
stn_estimates_.put(data_[window_pos_center], data_[window_pos_center].getIntensity() / noise);
// advance the window center by one datapoint
++window_pos_center;
++window_count;
} // end while
sparse_window_percent = sparse_window_percent * 100 / window_count;
histogram_oob_percent = histogram_oob_percent * 100 / window_count;
// warn if percentage of sparse windows is above 20%
if (sparse_window_percent > 20) {
System.err.println(
"WARNING in SignalToNoiseEstimatorMedian: "
+ sparse_window_percent
+ "% of all windows were sparse. You should consider increasing WindowLength or decreasing MinReqElementsInWindow");
}
// warn if percentage of possibly wrong median estimates is above 1%
if (histogram_oob_percent > 1) {
System.err.println(
"WARNING in SignalToNoiseEstimatorMedian: "
+ histogram_oob_percent
+ "% of all Signal-to-Noise estimates are too high, because the median was found in the rightmost histogram-bin. "
+ "You should consider increasing MaxIntensity (and maybe BinCount with it, to keep bin width reasonable)");
}
} // end of shiftWindow_
