Method makeRangeGetSteps

ij/src/main/java/ij/gui/Plot.java:2245–2341

Calculate the actual range, major step interval and set variables for data <-> pixels scaling

()

	/** Calculate the actual range, major step interval and set variables for data <-> pixels scaling */
	double[] makeRangeGetSteps() {
		steps = new double[2];
		logXAxis = hasFlag(X_LOG_NUMBERS);
		logYAxis = hasFlag(Y_LOG_NUMBERS);

		for (int i=0; i<currentMinMax.length; i+=2) {  //for x and y direction
			boolean logAxis = hasFlag(i==0 ? X_LOG_NUMBERS : Y_LOG_NUMBERS);
			//don't zoom in too much (otherwise finite float precision becomes an issue)
			double range = currentMinMax[i+1]-currentMinMax[i];
			double mid = 0.5*(currentMinMax[i+1]+currentMinMax[i]);
			double relativeRange = Math.abs(range/mid);
			if (range != 0 && relativeRange<1e-4) {
				currentMinMax[i+1] = mid + 0.5*range*1e-4/relativeRange;
				currentMinMax[i] = mid - 0.5*range*1e-4/relativeRange;
			}
			//no log range if range is too small or not positive values
			if (logAxis) {
				double rangeRatio = currentMinMax[i+1]/currentMinMax[i];
				if (!(rangeRatio > MIN_LOG_RATIO || 1./rangeRatio > MIN_LOG_RATIO) ||
					!(currentMinMax[i] > 10*Float.MIN_VALUE)  || !(currentMinMax[i+1] > 10*Float.MIN_VALUE))
				logAxis = false;
			}
			//for log axes, temporarily work on the logarithm
			if (logAxis) {
				currentMinMax[i] = Math.log10(currentMinMax[i]);
				currentMinMax[i+1] = Math.log10(currentMinMax[i+1]);
			}
			// calculate grid or major tick interval
			if ((i==0 && !simpleXAxis()) || (i==2 && !simpleYAxis())) {
				int minGridspacing = i==0 ? MIN_X_GRIDSPACING : MIN_Y_GRIDSPACING;
				int frameSize = i==0 ? frameWidth : frameHeight;
				double step = Tools.getNumberFromList(pp.frame.options, i==0 ? "xinterval=" : "yinterval="); //user-defined interval
				if (!Double.isNaN(step)) {
					int nSteps = (int)(Math.floor(currentMinMax[i+1]/step+1e-10) - Math.ceil(currentMinMax[i]/step-1e-10));
					if (nSteps < 1) step = Double.NaN;  //user-suppied interval too large, less than two numbers would be shown
					if ((i==0 && nSteps*sc(minGridspacing)*0.5 > frameSize) || i!=0 && nSteps*sc(pp.frame.getFont().getSize()) > frameSize)
						step = Double.NaN;              //user-suppied interval too small, too many numbers would be shown
				}
				if (Double.isNaN(step)) {               //automatic interval
					step = Math.abs((currentMinMax[i+1] - currentMinMax[i]) *
						Math.max(1.0/maxIntervals, (float)sc(minGridspacing)/frameSize+(maxIntervals>12 ? 0.02 : 0.06))); //the smallest allowable step
					step = niceNumber(step);
				}
				if (logAxis && step < 1)
					step = 1;
				steps[i/2] = step;
				//modify limits to grid or minor ticks if desired
				boolean force2grid = hasFlag(i==0 ? X_FORCE2GRID : Y_FORCE2GRID) && !ignoreForce2Grid;
				if (force2grid) {
					int i1 = (int)Math.floor(Math.min(currentMinMax[i],currentMinMax[i+1])/step+1.e-10);
					int i2 = (int)Math.ceil (Math.max(currentMinMax[i],currentMinMax[i+1])/step-1.e-10);
					if (currentMinMax[i+1] > currentMinMax[i]) {	// care about inverted axes with max<min
						currentMinMax[i] = i1 * step;
						currentMinMax[i+1] = i2 * step;
					} else {
						currentMinMax[i] = i2 * step;
						currentMinMax[i+1] = i1 * step;
					}