iOS Core Plot Library

Application needs to create an instance of CPTGraphHostingView which is hosting the graph view. In this class, there is hostedGraph which is an instance of CPTGraph which is a generic interface. In this case, we can have the CPTXYGraph  instance which is Bar chart kind of graph. 

    CPTXYGraph *barChart = [[CPTXYGraph alloc] initWithFrame:CGRectZero];

    barGraph.hostedGraph             = barChart;

    barGraph.allowPinchScaling = NO;

    

    barChart.paddingLeft   = 35.0;

    barChart.paddingTop    = 20.0;

    barChart.paddingRight  = 20.0;

We can also apply a theme for the graph using the below statements 

 CPTTheme *theme = [CPTTheme themeNamed:kCPTPlainBlackTheme];

    [barChart applyTheme:theme];

    

    barChart.plotAreaFrame.masksToBorder = NO;

    barChart.plotAreaFrame.borderLineStyle = nil;

The Axis style can be set like below     

CPTMutableLineStyle *majorGridLineStyle = [CPTMutableLineStyle lineStyle];

    majorGridLineStyle.lineWidth            = 0.1;

    majorGridLineStyle.lineColor            = [[CPTColor whiteColor] col

We can give the Axis labels like this below 

CPTAxisLabel *newLabel = [[CPTAxisLabel alloc] initWithText:[months objectAtIndex:labelLocation++] textStyle:x.labelTextStyle];

        newLabel.tickLocation = [tickLocation decimalValue];

        newLabel.offset       = x.labelOffset + x.majorTickLength;

        [customLabels addObject:newLabel];

 x.axisLabels = [NSSet setWithArray:customLabels];

Now we can draw each of the bar like in the below code

CPTBarPlot *barPlot = [[CPTBarPlot alloc] init];

    barPlot.fill = [CPTFill fillWithColor:[CPTColor colorWithComponentRed:87/255.0 green:142/255.0 blue:242/255.0 alpha:1.0]];

    barPlot.dataSource      = self;

    barPlot.barCornerRadius = 2.0f;

    barPlot.delegate        = self;

    barPlot.lineStyle = barLineStyle;

    barPlot.baseValue = CPTDecimalFromFloat(0.0f);

Application needs to implement the methods of CPTPlotDataSource so that the bar is supplied with the data 

The only mandatory method is 

-(NSUInteger)numberOfRecordsForPlot:(CPTPlot *)plot;

Other methods such as below are optional in the API

-(NSArray *)numbersForPlot:(CPTPlot *)plot field:(NSUInteger)fieldEnum recordIndexRange:(NSRange)indexRange;

-(NSNumber *)numberForPlot:(CPTPlot *)plot field:(NSUInteger)fieldEnum recordIndex:(NSUInteger)idx;

-(double *)doublesForPlot:(CPTPlot *)plot field:(NSUInteger)fieldEnum recordIndexRange:(NSRange)indexRange;

-(double)doubleForPlot:(CPTPlot *)plot field:(NSUInteger)fieldEnum recordIndex:(NSUInteger)idx;

-(CPTNumericData *)dataForPlot:(CPTPlot *)plot field:(NSUInteger)fieldEnum recordIndexRange:(NSRange)indexRange;

-(CPTNumericData *)dataForPlot:(CPTPlot *)plot recordIndexRange:(NSRange)indexRange;

-(NSArray *)dataLabelsForPlot:(CPTPlot *)plot recordIndexRange:(NSRange)indexRange;

-(CPTLayer *)dataLabelForPlot:(CPTPlot *)plot recordIndex:(NSUInteger)idx;

references:
http://www.raywenderlich.com/13269/how-to-draw-graphs-with-core-plot-part-1